feat: add image-blast-export skill (usdz, stl, fbx)

[mvanhorn]

Summary

A new image-blast-export skill converts generated .glb objects to USDZ (Apple AR / Vision Pro), STL (3D printing), and optionally FBX (Unity / Unreal, behind a --via blender flag).

Why this matters

The README markets image-blaster as embeddable in Unity, Unreal, Godot, Blender, Three.js, and Electron. Today the per-object output is .glb and .obj only. That covers Three.js and Godot but not Unity/Unreal (which want FBX), not Vision Pro / AR Quick Look (which wants USDZ), and not 3D printing (which wants STL). This skill closes that gap with a pure-JS path for USDZ + STL and an opt-in path for FBX.

Source	Evidence
Meshy image-to-3D features page	Meshy exports 7 formats including GLB, OBJ, FBX, STL, USDZ
Tripo3D multi-format export strategy	FBX for Unity, USDZ for AR, USD for Vision Pro, GLB for web
Threedium: Export Image-To-3D for Unity	Unity preferring FBX with PBR materials

Demo

Simulated demo (HyperFrames):

The terminal scene shows the actual smoke test output: butterfly.glb (from app/public/butterfly/) converts to a 46.1 KB USDZ and a 15.5 KB STL.

Changes

• .claude/skills/image-blast-export/SKILL.md plus matching image-blast-export.md agent
• .claude/scripts/asset-pipeline/convert-mesh.mjs -- pure-Node converter using three-stdlib's GLTFLoader, USDZExporter, STLExporter against the local .glb
• FBX is gated behind --via blender: when present and blender is on PATH, the script shells out via bpy.ops.import_scene.gltf + bpy.ops.export_scene.fbx. Without --via blender or without blender on PATH, FBX is skipped with a one-line warning (not a hard fail)
• three and three-stdlib added to root devDependencies so the script runs from the repo root (versions match app/package.json)
• Indexed file convention preserved: outputs are N-<slug>.usdz, N-<slug>.stl, with .N-<slug>-<fmt>-request.json provenance beside each
• README Advanced section updated; .claude/settings.json allow-list refreshed for the new skill + script

Testing

Smoke-tested locally against app/public/butterfly/butterfly.glb:

$ node .claude/scripts/asset-pipeline/convert-mesh.mjs \
    --input app/public/butterfly/butterfly.glb \
    --output-dir /tmp/convert-smoke \
    --formats usdz,stl --asset-name butterfly
{
  "outputs": [
    { "format": "usdz", "path": "/tmp/convert-smoke/0-butterfly.usdz" },
    { "format": "stl",  "path": "/tmp/convert-smoke/0-butterfly.stl"  }
  ],
  "skipped": []
}

Result: 0-butterfly.usdz (46.1 KB) and 0-butterfly.stl (15.5 KB) plus matching .0-butterfly-<fmt>-request.json provenance files. node --check passes on convert-mesh.mjs. FBX gracefully skips when blender is not on PATH.

AI was used for assistance.