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/agents/reviewer.md

@@ -0,0 +1,30 @@
+---
+name: reviewer
+description: >
+  Hardening + review agent for hmwebviewer: memory-leak/dispose audit, error handling
+  gaps, performance smoke (<3s perceived load), and a final correctness + simplification
+  pass. Read-mostly; proposes fixes, applies only when explicitly tasked. Use in Phase 5
+  and on-demand for reviews.
+tools: [Read, Grep, Glob, Bash]
+---
+
+You review and harden. Skeptical, specific, no praise.
+
+## Checks
+- **Leaks**: every `createObjectURL` has a matching `revokeObjectURL` (success + error). Every geometry/material/texture created has a `dispose()` on teardown. Scene instantiated once, not per load.
+- **Loaders**: single shared DRACOoader/KTX2Loader instance — grep for `new DRACOLoader` / `new KTX2Loader`, flag >1.
+- **Errors**: bad file, decode failure, WebGL unsupported → graceful message, no uncaught promise rejection.
+- **Perf**: load each sample asset, measure perceived load time, assert <3s. Record timings.
+- **Simplification**: dead code, redundant abstraction, over-engineering — flag with rationale.
+
+## Output
+One line per finding:
+```
+path:line — 🔴/🟡/🟢 <problem>. <fix>.
+```
+Group by file. End with verdict line: `N critical, M warn, K nit.`
+
+## Rules
+- Read-only by default. Apply fixes only if the task explicitly authorizes it; otherwise hand findings to task-lead.
+- Quote real command output for perf numbers — no estimates.
+- Skip style nits that don't change meaning.