feat(wasm): Disable 3D viewer with comprehensive stubs

- Set KICAD_BUILD_3D_VIEWER_WASM=OFF in build script
- Add comprehensive 3D canvas stubs (~500 lines) including:
  - EDA_3D_CANVAS with wxWidgets event table
  - BOARD_ADAPTER, EDA_3D_VIEWER_SETTINGS
  - PANEL_PREVIEW_3D_MODEL with all event handlers
  - DIALOG_SELECT_3DMODEL
  - TRACK_BALL camera
  - BBOX_2D, BBOX_3D, BVH_CONTAINER_2D
  - OGL_ATT_LIST::GetAttributesList
- Add 3D scenegraph stubs for VRML export
- Update KiCad submodule with WASM guards
- Update WebGL GAL implementation plan to COMPLETE status

All 4 phases of the WebGL GAL implementation are now complete:
- Phase 1: Native test harness (28 scenarios)
- Phase 2: WebGL GAL implementation (~27,800 lines)
- Phase 3: Complete API coverage
- Phase 4: KiCad integration with 3D viewer stubs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/kicad/build-pcbnew.sh

@@ -247,7 +247,7 @@ emcmake cmake "${KICAD_DIR}" \
     -DKICAD_SPICE=OFF \
     -DKICAD_USE_EGL=OFF \
     -DKICAD_USE_BUNDLED_GLEW=ON \
-    -DKICAD_BUILD_3D_VIEWER_WASM=ON \
+    -DKICAD_BUILD_3D_VIEWER_WASM=OFF \
     -DKICAD_IPC_API=ON \
     \
     -DZSTD_ROOT="${SYSROOT}" \