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/samples/Cube.dae

@@ -0,0 +1,62 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Cube.dae - hand-authored minimal COLLADA 1.4.1 unit cube for hmwebviewer ColladaLoader testing.
+     Single <geometry> (8 verts, 12 triangles) in one <visual_scene>. Edge length 2 (range -1..1),
+     centered at origin. Works for Path A (SSR ?model=) and Path B (drag & drop). No network required. -->
+<COLLADA xmlns="http://www.collada.org/2005/11/COLLADASchema" version="1.4.1">
+  <asset>
+    <contributor>
+      <author>hmwebviewer</author>
+      <authoring_tool>hand-authored</authoring_tool>
+    </contributor>
+    <created>2026-06-19T00:00:00Z</created>
+    <modified>2026-06-19T00:00:00Z</modified>
+    <unit name="meter" meter="1"/>
+    <up_axis>Y_UP</up_axis>
+  </asset>
+
+  <library_geometries>
+    <geometry id="Cube-mesh" name="Cube">
+      <mesh>
+        <source id="Cube-positions">
+          <float_array id="Cube-positions-array" count="24">
+            -1 -1 -1  -1 -1 1  -1 1 -1  -1 1 1  1 -1 -1  1 -1 1  1 1 -1  1 1 1
+          </float_array>
+          <technique_common>
+            <accessor source="#Cube-positions-array" count="8" stride="3">
+              <param name="X" type="float"/>
+              <param name="Y" type="float"/>
+              <param name="Z" type="float"/>
+            </accessor>
+          </technique_common>
+        </source>
+        <vertices id="Cube-vertices">
+          <input semantic="POSITION" source="#Cube-positions"/>
+        </vertices>
+        <triangles count="12">
+          <input semantic="VERTEX" source="#Cube-vertices" offset="0"/>
+          <p>
+            0 1 3  0 3 2
+            4 6 7  4 7 5
+            0 4 5  0 5 1
+            2 3 7  2 7 6
+            0 2 6  0 6 4
+            1 5 7  1 7 3
+          </p>
+        </triangles>
+      </mesh>
+    </geometry>
+  </library_geometries>
+
+  <library_visual_scenes>
+    <visual_scene id="Scene" name="Scene">
+      <node id="Cube" name="Cube" type="NODE">
+        <matrix sid="transform">1 0 0 0  0 1 0 0  0 0 1 0  0 0 0 1</matrix>
+        <instance_geometry url="#Cube-mesh" name="Cube"/>
+      </node>
+    </visual_scene>
+  </library_visual_scenes>
+
+  <scene>
+    <instance_visual_scene url="#Scene"/>
+  </scene>
+</COLLADA>