feat: multi-format 3D viewer with large-file OBJ streaming, Z-up, projection/outline UI

Three.js viewer supporting glb/gltf/obj/fbx/dae/ifc/ply via both server (SSR)
and drag&drop (CSR) paths.

- Streaming OBJ parser (src/viewer/objStream.ts) for files past the V8 max
  string length (>~1GB text) that OBJLoader can't handle; indexed geometry,
  per-vertex color from MTL Kd, float64 recenter baked in.
- In-viewer float64 recenter (objRecenter.ts) for huge CAD/survey coordinates
  (~1e8) so float32 vertex buffers keep precision (no cracked faces).
- Z-up right-handed world; Y-up formats rotated on load.
- OBJ+MTL+texture drag&drop (LoadingManager URL-modifier maps dropped images).
- OrbitControls ground-plane panning (road/rail alignment workflow).
- UI: Zoom Fit, perspective/orthographic toggle, feature-edge outline.
- DoubleSide for CAD OBJ; PLY mesh + point-cloud support.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/commands/optimize-asset.md

@@ -0,0 +1,13 @@
+---
+description: Run the offline asset optimization pipeline (gltf-transform Draco + KTX2) on a GLB file. Optionally pre-render a 360 WebP placeholder.
+---
+
+Asset path required: $ARGUMENTS  (e.g. `/optimize-asset samples/robot.glb`)
+
+Steps:
+1. Confirm `tools/preprocess.mjs` exists; if not, delegate to the `asset-pipeline` agent to build it first.
+2. Run the compressor on the input GLB → output to `samples/<name>.optimized.glb`. Print before/after sizes and the reduction %.
+3. If a second arg `--prerender` is given, also run the 360° pre-render pipeline to produce `public/previews/<name>.webp`.
+4. Verify the optimized GLB still loads in the viewer (load test).
+
+If `gltf-transform` or `toktx` (KTX2 encoder) is missing, report the install command and stop — do not silently skip.