feat(gltf): glTF/GLB scene loader with lighting, materials & 3D bounds

[obiot]

What

Adds a glTF / GLB scene loader to melonJS. Author a 3D scene in Blender (or any DCC tool), export a .glb, and load the whole thing with one call — exactly like a Tiled map:

me.loader.preload([{ name: "level", type: "glb", src: "models/level.glb" }], () => {
  me.level.load("level", { scale: 32 });   // meshes instantiated, lit by the authored sun
});

This is part 1 of the 19.8 glTF work; node/TRS animation lands in a focused follow-up PR before the 19.8 tag.

Highlights

• Loader — .glb/.gltf auto-registers with the level director; each mesh node → a Mesh under Camera3d. Parses the node graph, POSITION/NORMAL/TEXCOORD_0/COLOR_0/indices, baseColorTexture + baseColorFactor, perspective cameras, scene bounds, and KHR_lights_punctual lights. loader.getGLTF(name) exposes the raw descriptor. Uint32 index buffers preserved (>65535-vertex meshes).
• 3D mesh lighting — Light3d + LightingEnvironment (directional, half-Lambert + ambient), auto-loaded from the scene's authored sun. Opt-in mesh.lit routes to a dedicated LitMeshBatcher, so standalone unlit meshes stay on the lean path.
• Material color — baseColorFactor → tint (solid-color untextured materials no longer render white); vertex colors (COLOR_0). Compose factor × vertexColor × texel, under lighting.
• 3D bounds — Mesh.getBounds3d(), Camera3d.worldToScreen(), AABB3d exported (+ fromVertices), vertex.ts transformedBounds/boundingRadius.
• Render fix — world-space meshes no longer leak the anchor-point offset into the mesh view matrix (Renderable.applyAnchorTransform); props were rendering at the wrong position under Camera3d, sinking into the surfaces they rested on.
• @melonjs/debug-plugin 16.1.0 — 3D bounding-box wireframe overlay for meshes (requires melonJS ≥ 19.8).
• New "glTF Scene" example (Kenney Platformer Kit, CC0).

Tests

~50 new tests (parser, lighting, materials/vertex colors, bounds, worldToScreen, the anchor fix). Full suite green (4140 passed). Verified end-to-end via Playwright/ANGLE.

Docs

Wiki updated (Loading glTF / GLB scenes, Working in 3D) + README + CHANGELOG.

🤖 Generated with Claude Code