feat(UC-02): data-driven room themes — 6 JSON + consumer migration + cleanup

Phase 3: Extract 6 themes into JSON (oubliette, inferno, crypt, ice, sculk, sandstone)
Phase 4: Migrate HangingCagePiece to use RoomThemeRegistry.pickRandomOrFallback()
  - Move 7 shared static methods from RoomTheme into HangingCagePiece
  - Replace per-enum placeDecorations() with generic DecorationConfig-based placement
Phase 5: Delete RoomTheme.java (-1368L)

src/main/java/com/tiedup/remake/worldgen/HangingCagePiece.java

@@ -26,6 +26,7 @@ import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.WorldGenLevel;
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.ChestBlock;
+import net.minecraft.world.level.block.LanternBlock;
 import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.block.entity.RandomizableContainerBlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
@@ -279,7 +280,7 @@ public class HangingCagePiece extends StructurePiece {
 
     /**
      * Fallback: carve a 13x13x12 dungeon room and place the cage inside.
-     * Randomly selects a theme (Oubliette/Inferno) and layout (Square/Octagonal).
+     * Randomly selects a data-driven theme and layout (Square/Octagonal).
      */
     private void carveAndPlaceRoom(
         WorldGenLevel level,
@@ -288,9 +289,7 @@ public class HangingCagePiece extends StructurePiece {
         int centerZ,
         BoundingBox chunkBB
     ) {
-        RoomTheme theme = RoomTheme.values()[random.nextInt(
-            RoomTheme.values().length
-        )];
+        RoomThemeDefinition theme = RoomThemeRegistry.pickRandomOrFallback(random);
         RoomLayout layout = RoomLayout.values()[random.nextInt(
             RoomLayout.values().length
         )];
@@ -358,62 +357,24 @@ public class HangingCagePiece extends StructurePiece {
             }
         }
 
-        theme.placeDecorations(
-            level,
-            random,
-            baseX,
-            baseZ,
-            floorY,
-            layout,
-            chunkBB
+        placeThemeDecorations(
+            level, random, baseX, baseZ, floorY, layout, chunkBB, theme
         );
 
-        RoomTheme.placeSharedPillars(
-            level,
-            random,
-            baseX,
-            baseZ,
-            floorY,
-            layout,
-            theme,
-            chunkBB
+        placeSharedPillars(
+            level, random, baseX, baseZ, floorY, layout, theme, chunkBB
         );
-        RoomTheme.placeSharedFloorScatter(
-            level,
-            random,
-            baseX,
-            baseZ,
-            floorY,
-            layout,
-            theme,
-            chunkBB
+        placeSharedFloorScatter(
+            level, random, baseX, baseZ, floorY, layout, theme, chunkBB
         );
-        RoomTheme.placeSharedCeilingDecor(
-            level,
-            random,
-            baseX,
-            baseZ,
-            floorY,
-            layout,
-            chunkBB
+        placeSharedCeilingDecor(
+            level, random, baseX, baseZ, floorY, layout, chunkBB
         );
-        RoomTheme.placeSharedWallLighting(
-            level,
-            random,
-            baseX,
-            baseZ,
-            floorY,
-            layout,
-            chunkBB
+        placeSharedWallLighting(
+            level, random, baseX, baseZ, floorY, layout, chunkBB
         );
-        RoomTheme.placeSharedWallBands(
-            level,
-            baseX,
-            baseZ,
-            floorY,
-            layout,
-            theme,
-            chunkBB
+        placeSharedWallBands(
+            level, baseX, baseZ, floorY, layout, theme, chunkBB
         );
 
         placeVanillaChest(level, random, baseX, baseZ, floorY, layout, chunkBB);
@@ -451,7 +412,7 @@ public class HangingCagePiece extends StructurePiece {
 
         TiedUpMod.LOGGER.info(
             "[HangingCage] Placed cage in carved room (theme={}, layout={}) at {}",
-            theme.name(),
+            theme.id(),
             layout.name(),
             masterPos.toShortString()
         );
@@ -655,4 +616,318 @@ public class HangingCagePiece extends StructurePiece {
             );
         }
     }
+
+    // ── Data-driven theme decorations ───────────────────────────────
+
+    /**
+     * Place decorations from the data-driven {@link DecorationConfig}.
+     * Replaces the old per-enum {@code RoomTheme.placeDecorations()} method.
+     */
+    private static void placeThemeDecorations(
+        WorldGenLevel level,
+        RandomSource random,
+        int baseX,
+        int baseZ,
+        int floorY,
+        RoomLayout layout,
+        BoundingBox chunkBB,
+        RoomThemeDefinition theme
+    ) {
+        DecorationConfig deco = theme.decorations();
+        int[][] corners = layout.innerCorners();
+
+        // Corner decorations (e.g. cobwebs low+high, soul fire, snow layers)
+        for (DecorationConfig.PositionedBlock pb : deco.cornerDecorations()) {
+            for (int[] c : corners) {
+                if (layout.isInShape(c[0], c[1]) && !layout.isWall(c[0], c[1])) {
+                    safeSetBlock(level,
+                        new BlockPos(baseX + c[0], floorY + pb.yOffset(), baseZ + c[1]),
+                        pb.state(), chunkBB);
+                }
+            }
+        }
+
+        // Wall midpoint decorations (e.g. soul lanterns, crying obsidian, sculk veins)
+        int[][] wallMidpoints = {{6, 1}, {6, 11}, {1, 6}, {11, 6}};
+        for (DecorationConfig.PositionedBlock pb : deco.wallMidpointBlocks()) {
+            for (int[] wp : wallMidpoints) {
+                if (layout.isWall(wp[0], wp[1])) {
+                    safeSetBlock(level,
+                        new BlockPos(baseX + wp[0], floorY + pb.yOffset(), baseZ + wp[1]),
+                        pb.state(), chunkBB);
+                }
+            }
+        }
+
+        // First corner special (e.g. water cauldron, skull, TNT, sculk catalyst)
+        if (deco.firstCornerSpecial() != null && corners.length > 0) {
+            int[] sc = corners[0];
+            if (layout.isInShape(sc[0], sc[1]) && !layout.isWall(sc[0], sc[1])) {
+                safeSetBlock(level,
+                    new BlockPos(baseX + sc[0], floorY + deco.firstCornerSpecial().yOffset(), baseZ + sc[1]),
+                    deco.firstCornerSpecial().state(), chunkBB);
+            }
+        }
+
+        // Furniture cluster at corners[1] (e.g. barrel+brewing_stand, soul_campfire+cauldron)
+        if (corners.length > 1) {
+            int[] fc = corners[1];
+            int fcx = fc[0] + (fc[0] < 6 ? 1 : -1);
+            int fcz = fc[1] + (fc[1] < 6 ? 1 : -1);
+            if (layout.isInShape(fcx, fcz) && !layout.isWall(fcx, fcz)) {
+                for (DecorationConfig.PositionedBlock pb : deco.furnitureCluster()) {
+                    safeSetBlock(level,
+                        new BlockPos(baseX + fcx, floorY + pb.yOffset(), baseZ + fcz),
+                        pb.state(), chunkBB);
+                }
+            }
+
+            // Ceiling chain above furniture
+            if (deco.hasCeilingChain()) {
+                for (int cy = 8; cy <= 10; cy++) {
+                    safeSetBlock(level,
+                        new BlockPos(baseX + fcx, floorY + cy, baseZ + fcz),
+                        Blocks.CHAIN.defaultBlockState(), chunkBB);
+                }
+            }
+        }
+
+        // Torch lighting (wall torches at outer wall midpoints) -- used by Crypt, Sandstone
+        if (deco.useTorchLighting()) {
+            for (int[] wallPos : new int[][] {{6, 0}, {6, 12}, {0, 6}, {12, 6}}) {
+                if (layout.isWall(wallPos[0], wallPos[1])) {
+                    Direction torchDir = getTorchDirection(wallPos[0], wallPos[1]);
+                    if (torchDir != null) {
+                        safeSetBlock(level,
+                            new BlockPos(baseX + wallPos[0], floorY + 3, baseZ + wallPos[1]),
+                            Blocks.WALL_TORCH.defaultBlockState().setValue(
+                                net.minecraft.world.level.block.WallTorchBlock.FACING, torchDir),
+                            chunkBB);
+                    }
+                }
+            }
+        }
+
+        // Side chains + hanging lanterns (shared by all themes)
+        placeSharedChains(level, baseX, baseZ, floorY, chunkBB);
+        placeSharedHangingLanterns(level, baseX, baseZ, floorY, chunkBB);
+    }
+
+    // ── Shared structural features (moved from RoomTheme) ──────────
+
+    /** Pillar positions -- verified to be inside all 4 layouts. */
+    private static final int[][] PILLAR_POSITIONS = {
+        {4, 4}, {4, 8}, {8, 4}, {8, 8},
+    };
+
+    /** Place 4 full-height pillars at verified positions. */
+    private static void placeSharedPillars(
+        WorldGenLevel level,
+        RandomSource random,
+        int baseX,
+        int baseZ,
+        int floorY,
+        RoomLayout layout,
+        RoomThemeDefinition theme,
+        BoundingBox chunkBB
+    ) {
+        for (int[] p : PILLAR_POSITIONS) {
+            if (!layout.isInShape(p[0], p[1]) || layout.isWall(p[0], p[1])) continue;
+            for (int ry = 1; ry <= 10; ry++) {
+                safeSetBlock(level,
+                    new BlockPos(baseX + p[0], floorY + ry, baseZ + p[1]),
+                    theme.pillarBlock(random, ry), chunkBB);
+            }
+        }
+    }
+
+    /** Place random floor scatter (~12% of interior positions). */
+    private static void placeSharedFloorScatter(
+        WorldGenLevel level,
+        RandomSource random,
+        int baseX,
+        int baseZ,
+        int floorY,
+        RoomLayout layout,
+        RoomThemeDefinition theme,
+        BoundingBox chunkBB
+    ) {
+        for (int rx = 1; rx <= 11; rx++) {
+            for (int rz = 1; rz <= 11; rz++) {
+                if (!layout.isInShape(rx, rz) || layout.isWall(rx, rz)) continue;
+                // Skip pillar positions
+                if ((rx == 4 || rx == 8) && (rz == 4 || rz == 8)) continue;
+                // Skip cage center area (5-7, 5-7)
+                if (rx >= 5 && rx <= 7 && rz >= 5 && rz <= 7) continue;
+                // Skip corner positions (used by decorations/chests)
+                if ((rx <= 2 || rx >= 10) && (rz <= 2 || rz >= 10)) continue;
+                if (random.nextFloat() < 0.12f) {
+                    BlockState scatter = theme.scatterBlock(random);
+                    if (scatter != null) {
+                        safeSetBlock(level,
+                            new BlockPos(baseX + rx, floorY + 1, baseZ + rz),
+                            scatter, chunkBB);
+                    }
+                }
+            }
+        }
+    }
+
+    /** Place ceiling cobwebs and extra hanging chains. */
+    private static void placeSharedCeilingDecor(
+        WorldGenLevel level,
+        RandomSource random,
+        int baseX,
+        int baseZ,
+        int floorY,
+        RoomLayout layout,
+        BoundingBox chunkBB
+    ) {
+        // Cobwebs along walls at ceiling level
+        int[][] cobwebCandidates = {
+            {2, 1}, {4, 1}, {8, 1}, {10, 1},
+            {2, 11}, {4, 11}, {8, 11}, {10, 11},
+            {1, 4}, {1, 8}, {11, 4}, {11, 8},
+        };
+        for (int[] pos : cobwebCandidates) {
+            if (layout.isInShape(pos[0], pos[1])
+                && !layout.isWall(pos[0], pos[1])
+                && random.nextFloat() < 0.45f) {
+                safeSetBlock(level,
+                    new BlockPos(baseX + pos[0], floorY + 10, baseZ + pos[1]),
+                    Blocks.COBWEB.defaultBlockState(), chunkBB);
+            }
+        }
+        // Extra hanging chains at random interior positions
+        int[][] chainCandidates = {{5, 3}, {7, 9}, {3, 7}};
+        for (int[] pos : chainCandidates) {
+            if (layout.isInShape(pos[0], pos[1])
+                && !layout.isWall(pos[0], pos[1])
+                && random.nextFloat() < 0.6f) {
+                safeSetBlock(level,
+                    new BlockPos(baseX + pos[0], floorY + 10, baseZ + pos[1]),
+                    Blocks.CHAIN.defaultBlockState(), chunkBB);
+                safeSetBlock(level,
+                    new BlockPos(baseX + pos[0], floorY + 9, baseZ + pos[1]),
+                    Blocks.CHAIN.defaultBlockState(), chunkBB);
+            }
+        }
+    }
+
+    /** Place additional wall-mounted lighting. */
+    private static void placeSharedWallLighting(
+        WorldGenLevel level,
+        RandomSource random,
+        int baseX,
+        int baseZ,
+        int floorY,
+        RoomLayout layout,
+        BoundingBox chunkBB
+    ) {
+        // Lanterns on pillar sides (facing center) at ry=1 (on the floor)
+        int[][] pillarLanternPositions = {
+            {5, 4}, {4, 7}, {8, 5}, {7, 8},
+        };
+        for (int[] pos : pillarLanternPositions) {
+            if (layout.isInShape(pos[0], pos[1])
+                && !layout.isWall(pos[0], pos[1])) {
+                safeSetBlock(level,
+                    new BlockPos(baseX + pos[0], floorY + 1, baseZ + pos[1]),
+                    Blocks.LANTERN.defaultBlockState(), chunkBB);
+            }
+        }
+        // Extra wall sconces at quarter-points
+        int[][] wallSconces = {
+            {4, 0}, {8, 0}, {4, 12}, {8, 12},
+            {0, 4}, {0, 8}, {12, 4}, {12, 8},
+        };
+        for (int[] pos : wallSconces) {
+            if (layout.isWall(pos[0], pos[1]) && random.nextFloat() < 0.5f) {
+                Direction torchDir = getTorchDirection(pos[0], pos[1]);
+                if (torchDir != null) {
+                    safeSetBlock(level,
+                        new BlockPos(baseX + pos[0], floorY + 3, baseZ + pos[1]),
+                        Blocks.WALL_TORCH.defaultBlockState().setValue(
+                            net.minecraft.world.level.block.WallTorchBlock.FACING, torchDir),
+                        chunkBB);
+                }
+            }
+        }
+    }
+
+    /** Place wall accent bands at ry=5 and ry=8. */
+    private static void placeSharedWallBands(
+        WorldGenLevel level,
+        int baseX,
+        int baseZ,
+        int floorY,
+        RoomLayout layout,
+        RoomThemeDefinition theme,
+        BoundingBox chunkBB
+    ) {
+        int[][] bandPositions = {
+            {6, 1}, {6, 11}, {1, 6}, {11, 6},
+            {4, 1}, {8, 1}, {4, 11}, {8, 11},
+            {1, 4}, {1, 8}, {11, 4}, {11, 8},
+        };
+        for (int[] pos : bandPositions) {
+            if (layout.isWall(pos[0], pos[1])) {
+                // Band at ry=5
+                safeSetBlock(level,
+                    new BlockPos(baseX + pos[0], floorY + 5, baseZ + pos[1]),
+                    theme.wallAccentBlock(), chunkBB);
+                // Optional band at ry=8
+                safeSetBlock(level,
+                    new BlockPos(baseX + pos[0], floorY + 8, baseZ + pos[1]),
+                    theme.wallAccentBlock(), chunkBB);
+            }
+        }
+    }
+
+    /** Chains on cage flanks and ceiling corners -- shared by all themes. */
+    private static void placeSharedChains(
+        WorldGenLevel level,
+        int baseX,
+        int baseZ,
+        int floorY,
+        BoundingBox chunkBB
+    ) {
+        for (int[] chainPos : new int[][] {{3, 6}, {9, 6}}) {
+            for (int ry = 5; ry <= 10; ry++) {
+                safeSetBlock(level,
+                    new BlockPos(baseX + chainPos[0], floorY + ry, baseZ + chainPos[1]),
+                    Blocks.CHAIN.defaultBlockState(), chunkBB);
+            }
+        }
+        for (int[] chainPos : new int[][] {{3, 3}, {3, 9}, {9, 3}, {9, 9}}) {
+            safeSetBlock(level,
+                new BlockPos(baseX + chainPos[0], floorY + 10, baseZ + chainPos[1]),
+                Blocks.CHAIN.defaultBlockState(), chunkBB);
+        }
+    }
+
+    /** Determine torch facing direction for a wall position (torch faces inward). */
+    private static Direction getTorchDirection(int rx, int rz) {
+        if (rz == 0) return Direction.SOUTH;
+        if (rz == 12) return Direction.NORTH;
+        if (rx == 0) return Direction.EAST;
+        if (rx == 12) return Direction.WEST;
+        return null;
+    }
+
+    /** Hanging lanterns -- shared by all themes. */
+    private static void placeSharedHangingLanterns(
+        WorldGenLevel level,
+        int baseX,
+        int baseZ,
+        int floorY,
+        BoundingBox chunkBB
+    ) {
+        for (int[] pos : new int[][] {{3, 3}, {9, 9}}) {
+            safeSetBlock(level,
+                new BlockPos(baseX + pos[0], floorY + 9, baseZ + pos[1]),
+                Blocks.LANTERN.defaultBlockState().setValue(LanternBlock.HANGING, true),
+                chunkBB);
+        }
+    }
 }