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>

public/basis/README.md

@@ -0,0 +1,46 @@
+# Basis Universal GPU Texture Compression
+
+Basis Universal is a "[supercompressed](http://gamma.cs.unc.edu/GST/gst.pdf)"
+GPU texture and texture video compression system that outputs a highly
+compressed intermediate file format (.basis) that can be quickly transcoded to
+a wide variety of GPU texture compression formats.
+
+[GitHub](https://github.com/BinomialLLC/basis_universal)
+
+## Transcoders
+
+Basis Universal texture data may be used in two different file formats:
+`.basis` and `.ktx2`, where `ktx2` is a standardized wrapper around basis texture data.
+
+For further documentation about the Basis compressor and transcoder, refer to
+the [Basis GitHub repository](https://github.com/BinomialLLC/basis_universal).
+
+The folder contains two files required for transcoding `.basis` or `.ktx2` textures:
+
+* `basis_transcoder.js` — JavaScript wrapper for the WebAssembly transcoder.
+* `basis_transcoder.wasm` — WebAssembly transcoder.
+
+Both are dependencies of `KTX2Loader`:
+
+```js
+const ktx2Loader = new KTX2Loader();
+ktx2Loader.setTranscoderPath( 'examples/jsm/libs/basis/' );
+ktx2Loader.detectSupport( renderer );
+ktx2Loader.load( 'diffuse.ktx2', function ( texture ) {
+
+	const material = new THREE.MeshStandardMaterial( { map: texture } );
+
+}, function () {
+
+	console.log( 'onProgress' );
+
+}, function ( e ) {
+
+	console.error( e );
+
+} );
+```
+
+## License
+
+[Apache License 2.0](https://github.com/BinomialLLC/basis_universal/blob/master/LICENSE)