tools: web viewer shows the owner's world; collapsible phone menu (W2)

export_world.py exports the owner four-strate world (LOD0-2 around each arrival + one FI
passage view) through the headless mesh exporter and converts to GLB (16-45 MB, 0.6-1.7M
triangles each); GLBs are git-ignored and regenerated by the script. Menu collapses to a
button (collapsed by default on phones), smaller phone controls, loading progress and errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

.gitignore

@@ -32,3 +32,7 @@
 /Standalone/data/*.err
 /Standalone/data/*.vfmesh
 /Standalone/Research/**/*.log
+
+# Web viewer world exports (regenerate with Standalone/Tools/webviewer/export_world.py)
+/Standalone/Tools/webviewer/meshes/*-arrival.glb
+/Standalone/Tools/webviewer/meshes/*-passage.glb