feat: WOM2 animated model format with bones and keyframe animation

Upgrades WOM from geometry-only (WOM1) to fully animated (WOM2):

- WOM2 magic (0x324D4F57) for animated models, WOM1 for static
- Vertex extended: +boneWeights[4] +boneIndices[4] (40 bytes vs 32)
- Bone data: keyBoneId, parentBone, pivot, flags per bone
- Animation data: per-sequence per-bone keyframes with translation,
  rotation (quaternion), scale at millisecond timestamps
- fromM2() now preserves all skeletal data: bone hierarchy, weights,
  and per-sequence keyframes from M2 animation tracks
- Backward compatible: WOM1 files load without bone data (32-byte
  vertices read and padded with default bone weights)
- FORMAT_SPEC.md updated with WOM2 binary layout

tools/editor/FORMAT_SPEC.md

@@ -20,10 +20,14 @@ Novel file formats for custom WoW zone content. No Blizzard IP.
 
 ## WOM — Wowee Open Model (binary)
 - Extension: `.wom`
-- Magic: `WOM1` (0x314D4F57)
+- Magic: `WOM1` (0x314D4F57) for static, `WOM2` (0x324D4F57) for animated
 - Layout: magic(4) + vertCount(4) + indexCount(4) + texCount(4) + bounds(28) + name + vertices + indices + texPaths
-- Vertex: position(vec3) + normal(vec3) + texCoord(vec2) = 32 bytes
-- Note: geometry-only (no skeletal animation — WOM2 planned for bone data)
+- WOM1 Vertex: position(vec3) + normal(vec3) + texCoord(vec2) = 32 bytes
+- WOM2 Vertex: + boneWeights(4) + boneIndices(4) = 40 bytes
+- WOM2 Bones: boneCount(4) + [keyBoneId(4) + parentBone(2) + pivot(12) + flags(4)] × N
+- WOM2 Animations: animCount(4) + [id(4) + duration(4) + speed(4) + per-bone keyframes] × N
+- Keyframe: timeMs(4) + translation(12) + rotation(16) + scale(12) = 44 bytes
+- Backward compatible: WOM1 files load without bone/animation data
 
 ## WOB — Wowee Open Building (binary)
 - Extension: `.wob`