feat(gltf): node animation + Sprite-aligned animation API; Light3d as a world renderable

[obiot]

Builds on the glTF/GLB scene loader (#1502) with node/TRS animation and unifies the 2D ↔ 3D animation and lighting APIs.

Animation

• glTF node animation — assets with animation channels load as a rig-driven GLTFModel that keeps the node hierarchy intact (an animated parent carries its children). Per-frame TRS sampling (LERP/SLERP/STEP; CUBICSPLINE value), allocation-free pose path (preallocated per-node world buffers). The parser emits the node graph + animation clips.
• Sprite-aligned API on both Sprite and GLTFModel via a shared parseAnimationOptions helper: setCurrentAnimation(name, { loop, speed, onComplete, next }), getAnimationNames, animationspeed, and play / pause / stop. Additive and non-breaking on Sprite (legacy string / function / no-arg forms preserved).

Lighting (unify 3D with 2D)

• Light3d is now a world Renderable, managed exactly like Light2d: world.addChild(new Light3d({ direction, color, intensity })) and the active stage auto-tracks it; ambient is a Light3d with type: "ambient". LightingEnvironment is removed (folded into the stage's active-light set + a packMeshLights helper).
• Both lights co-located in src/lighting/; Light2d converted to TypeScript to match Light3d.

Materials / loader

• Mesh.textureRepeat — honors the glTF sampler wrapS/wrapT (default REPEAT) so tiling UVs (authored outside [0,1]) sample correctly instead of clamping flat. Known limitation tracked in Mesh.textureRepeat mutates the shared per-image TextureAtlas.repeat (wrap mode is image-global) #1503.
• External glTF resources — external .bin buffers + image uris resolved relative to the asset URL, with crossOrigin forwarded.
• OBJ/MTL textures auto-load — preloadMTL loads each material's map_Kd relative to the .mtl (parity with the glTF external-texture path), so an OBJ model's textures come for free; preloading the model + material is enough. A missing texture is warned + skipped (white-pixel fallback), not fatal.

Fixes

• Camera3d.isVisible no longer NaN-culls sizeless grouping containers (and their whole subtree) — infinite-bounds containers are always visible (matches Camera2d).

Example

New glTF Animated Model example (Kenney Blocky Characters, CC0): walking character under Camera3d, clip selector + speed + play/pause/stop, and drag-to-orbit.

Tests / docs

• ~125 new tests (parser graph/animations/wrap + robustness, keyframe sampler, GLTFModel, lighting + packMeshLights, Sprite play/pause/stop, parseAnimationOptions, Camera3d infinite-bounds, Mesh.textureRepeat, OBJ map_Kd auto-load). Full suite 4239 passed / 15 skipped / 0 failed; lint + tsc + doc-gen clean.
• README, CHANGELOG (19.8), and the two 3D wiki pages updated (support matrices reformatted to feature → ✅/❌, modern named-import API style).

Related

• Closes OBJ/MTL: auto-load map_Kd textures relative to the .mtl (make the explicit texture preload optional) #1505 (OBJ/MTL map_Kd auto-load).
• Introduces/tracks Mesh.textureRepeat mutates the shared per-image TextureAtlas.repeat (wrap mode is image-global) #1503 (Mesh.textureRepeat shared-atlas wrap mode); related to TextureCache.get(image, frame): framewidth/frameheight refinement is a no-op for every atlas format #1489 / Refactor TextureCache and Batcher base class for renderer-agnostic abstraction #1410 (TextureCache refactor family).
• Does not address Add a 2.5D platformer example validating the Camera3d + Octree + SAT pattern #1476 (2.5D platformer Camera3d+Octree+SAT example) — natural follow-up.

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