fix(validation): reduce log spam + add OOM guard + check correct mesh for WEIGHTS_0

- DataDrivenItemParser: downgrade animation_bones absence log from INFO to
  DEBUG (was spamming for every item without the optional field)
- GlbValidator: read 12-byte GLB header first and reject files declaring
  totalLength > 50 MB before allocating (prevents OOM on malformed GLBs)
- GlbValidator: WEIGHTS_0 check now uses the same mesh selection logic as
  GlbParser (prefer "Item", fallback to last non-Player) instead of
  blindly checking the first mesh

docs/ARTIST_GUIDE.md

@@ -183,7 +183,8 @@ Weight paint your mesh to the skeleton bones it should follow.
 
 ### Rules
 
-- **Only paint to the 11 standard bones.** Any other bones in your Blender file will be ignored by the mod.
+- **Paint to the 11 standard bones** for parts that should follow the player's body.
+- **You can also use custom bones** for decorative elements like chains, ribbons, pendants, or twist bones. Custom bones follow their parent in the bone hierarchy (rest pose) — they won't animate independently, but they move with the body part they're attached to. This is useful for better weight painting and mesh deformation.
 - **Paint to the bones of your regions.** Handcuffs (ARMS region) should be weighted to `rightUpperArm`, `rightLowerArm`, `leftUpperArm`, `leftLowerArm`.
 - **You can paint to bones outside your regions** for smooth deformation. For example, handcuffs might have small weights on `body` near the shoulder area for smoother bending. This is fine — the weight painting is about mesh deformation, not animation control.
 - **Normalize your weights.** Each vertex's total weights across all bones must sum to 1.0. Blender does this by default.
@@ -193,6 +194,7 @@ Weight paint your mesh to the skeleton bones it should follow.
 - For rigid items (metal cuffs), use hard weights — each vertex fully assigned to one bone.
 - For flexible items (rope, leather), blend weights between adjacent bones for smooth bending.
 - The chain between handcuffs? Weight it 50/50 to both arms, or use a separate mesh element weighted to `body`.
+- Custom bones are great for chains, dangling locks, or decorative straps — add a bone parented to a standard bone, weight your mesh to it, and it'll follow the parent's movement automatically.
 
 ---
 
@@ -630,7 +632,8 @@ In your JSON definition, separate the mesh from the animations:
 - [ ] Actions are named `PlayerArmature|Idle`, `PlayerArmature|Struggle`, etc.
 - [ ] Mesh is weight-painted to skeleton bones only
 - [ ] Weights are normalized
-- [ ] No orphan bones (extra bones not in the standard 11 are ignored but add file size)
+- [ ] Custom bones (if any) are parented to a standard bone in the hierarchy
+- [ ] Your item mesh is named `Item` in Blender (recommended — ensures the mod picks the correct mesh if your file has multiple objects)
 - [ ] Materials/textures are applied (the GLB bakes them in)
 - [ ] Scale is correct (1 Blender unit = 1 Minecraft block = 16 pixels)
 
@@ -763,14 +766,16 @@ The `movement_style` changes how the player physically moves — slower speed, d
 | `movement_style` | string | No | Movement restriction: `"waddle"`, `"shuffle"`, `"hop"`, or `"crawl"` |
 | `movement_modifier` | object | No | Override speed/jump for the movement style (requires `movement_style`) |
 | `creator` | string | No | Author/creator name, shown in the item tooltip |
-| `animation_bones` | object | Yes | Per-animation bone whitelist (see below) |
+| `animation_bones` | object | No | Per-animation bone whitelist (see below). If omitted, all owned bones are enabled for all animations. |
 | `components` | object | No | Gameplay behavior components (see [Components](#components-gameplay-behaviors) below) |
 
-### animation_bones (required)
+### animation_bones (optional)
 
-Declares which bones each named animation is allowed to control for this item. This enables fine-grained per-animation bone filtering: an item might own `body` via its regions but only want the "idle" animation to affect the arms.
+Fine-grained control over which bones each animation is allowed to affect. Most items don't need this — if omitted, all owned bones (from your `regions`) are enabled for all animations automatically.
 
-**Format:** A JSON object where each key is an animation name (matching the GLB animation names) and each value is an array of bone names.
+**When to use it:** When your item owns bones via its regions but you only want specific animations to affect specific bones. For example, an item owning ARMS + TORSO might only want the "idle" pose to affect the arms, and only the "struggle" animation to also move the body.
+
+**Format:** A JSON object where each key is an animation name and each value is an array of bone names.
 
 **Valid bone names:** `head`, `body`, `rightArm`, `leftArm`, `rightLeg`, `leftLeg`
 
@@ -784,7 +789,7 @@ Declares which bones each named animation is allowed to control for this item. T
 
 At runtime, the effective bones for a given animation clip are computed as the **intersection** of `animation_bones[clipName]` and the item's owned parts (from region conflict resolution). If the clip name is not listed in `animation_bones`, the item falls back to using all its owned parts.
 
-This field is **required**. Items without `animation_bones` will be rejected by the parser.
+**If omitted entirely:** All owned bones are enabled for all animations. This is the correct default for most items — you only need `animation_bones` for advanced per-animation filtering.
 
 ### Components (Gameplay Behaviors)
 
@@ -1020,8 +1025,8 @@ Use your own namespace (e.g., `mycreator`) to avoid conflicts with the base mod
 
 | Mistake | Symptom | Fix |
 |---------|---------|-----|
-| Bone name typo (`RightUpperArm` instead of `rightUpperArm`) | Mesh doesn't follow that bone | Names are **camelCase**, not PascalCase. Check exact spelling. |
-| Extra bones in the armature | No visible issue (ignored), larger file | Delete non-standard bones before export |
+| Bone name typo (`RightUpperArm` instead of `rightUpperArm`) | Warning in log: "did you mean 'rightUpperArm'?" — bone treated as custom | Names are **camelCase**, not PascalCase. Check exact spelling. Run `/tiedup validate` to see warnings. |
+| Extra bones in the armature | Custom bones follow their parent in rest pose | Intentional custom bones are fine (chains, decorations). Unintentional ones add file size — delete them. |
 | Missing `PlayerArmature` root | Mesh renders at wrong position | Rename your armature root to `PlayerArmature` |
 | Animating `body` bone without TORSO region | Body keyframes used only if `body` is free (no other item owns it) | Declare TORSO/WAIST region if you always want to control body, or use `Full` animations for free-bone effects |
 
@@ -1041,7 +1046,7 @@ Use your own namespace (e.g., `mycreator`) to avoid conflicts with the base mod
 |---------|---------|-----|
 | Vertices not weighted to any bone | Part of mesh stays frozen in space | Weight paint everything to at least one bone |
 | Weights not normalized | Mesh stretches or compresses oddly | Blender > Weights > Normalize All |
-| Weighted to a non-standard bone | That part of mesh stays frozen | Only weight to the 11 standard bones |
+| Weighted to a non-standard bone | Mesh follows parent bone in rest pose | This is OK if intentional (custom bones). If not, re-weight to a standard bone. |
 
 ### JSON Issues