fix(animation): variant randomness no longer permanently cached + fix FullHead false-positive

Two fixes from the animation audit:

1. Variant cache key now includes the resolved animation name (e.g., Struggle.2).
   Previously, the cache key only used context+parts, so the first random variant
   pick was reused forever. Now each variant gets its own cache entry, and a fresh
   random pick happens each time the context changes.

2. FullHead check changed from contains("Head") to startsWith("gltf_FullHead")
   to prevent false positives on names like FullOverhead or FullAhead.

src/main/java/com/tiedup/remake/client/gltf/GltfAnimationApplier.java

@@ -126,11 +126,13 @@ public final class GltfAnimationApplier {
         String enabledKey = canonicalPartsKey(ownership.enabledParts());
         String partsKey = ownedKey + ";" + enabledKey;
 
-        // Build composite state key to avoid redundant updates
+        // Build composite state key to detect context changes.
+        // NOTE: This key does NOT include the variant name — that is resolved fresh
+        // each time the context changes, enabling random variant selection.
         String stateKey = animSource + "|" + context.name() + "|" + partsKey;
         String currentKey = activeStateKeys.get(entity.getUUID());
         if (stateKey.equals(currentKey)) {
-            return true; // Already active, no-op
+            return true; // Same context, same parts — no need to re-resolve
         }
 
         // === Layer 1: Context animation (base body posture) ===
@@ -153,8 +155,7 @@ public final class GltfAnimationApplier {
             return false;
         }
 
-        KeyframeAnimation itemAnim = itemAnimCache.get(itemCacheKey);
-        if (itemAnim == null) {
+        // Resolve animation data first (needed for variant resolution)
         GltfData animData = GlbAnimationResolver.resolveAnimationData(
             modelLoc,
             animationSource
@@ -168,11 +169,22 @@ public final class GltfAnimationApplier {
             activeStateKeys.put(entity.getUUID(), stateKey);
             return false;
         }
-            // Resolve which named animation to use (with fallback chain + variant selection)
+
+        // Resolve which named animation to use (with fallback chain + variant selection).
+        // This must happen BEFORE the cache lookup because variant selection is random —
+        // we want a fresh random pick each time the context changes, not a permanently
+        // cached first pick.
         String glbAnimName = GlbAnimationResolver.resolve(
             animData,
             context
         );
+
+        // Include the resolved animation name in the cache key so different variants
+        // (Struggle.1 vs Struggle.2) get separate cache entries.
+        String variantCacheKey = itemCacheKey + "#" + (glbAnimName != null ? glbAnimName : "default");
+
+        KeyframeAnimation itemAnim = itemAnimCache.get(variantCacheKey);
+        if (itemAnim == null) {
             // Pass both owned parts and enabled parts (owned + free) for selective enabling
             itemAnim = GltfPoseConverter.convertSelective(
                 animData,
@@ -180,7 +192,7 @@ public final class GltfAnimationApplier {
                 ownership.thisParts(),
                 ownership.enabledParts()
             );
-            itemAnimCache.put(itemCacheKey, itemAnim);
+            itemAnimCache.put(variantCacheKey, itemAnim);
         }
 
         BondageAnimationManager.playDirect(entity, itemAnim);

src/main/java/com/tiedup/remake/client/gltf/GltfPoseConverter.java

@@ -587,7 +587,10 @@ public final class GltfPoseConverter {
         // Head is protected by default — only enabled as a free bone when the animation
         // name contains "Head" (e.g., FullHeadStruggle, FullHeadIdle).
         // This lets artists opt-in per animation without affecting the item's regions.
-        boolean allowFreeHead = isFullBodyAnimation && animName.contains("Head");
+        // FullHead prefix (e.g., FullHeadStruggle) opts into head as a free bone.
+        // Use startsWith to avoid false positives (e.g., FullOverhead, FullAhead).
+        boolean allowFreeHead = isFullBodyAnimation &&
+            animName.startsWith("gltf_FullHead");
 
         String[] allParts = {
             "head",