Add KiCad PCBnew WASM build support and documentation

Build infrastructure:
- Update build-pcbnew.sh with stub library compilation
- Update build-wxuniversal-wasm.sh with library symlinks and stubs
- Add stub libraries for libgit2 and curl (network ops via JS)
- Add WASM-specific CMake Find modules

Documentation:
- Add KICAD_WASM_BUILD.md with complete modification list
- Document 68 KiCad files modified for WASM support
- Document disabled features and reasons
- Document stub libraries and wxWidgets changes

Submodule updates:
- kicad: Add WASM/Emscripten build support (wasm-port branch)
- wxwidgets: Add KiCad compatibility fixes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

scripts/build-wxuniversal-wasm.sh

@@ -95,6 +95,27 @@ echo ""
 echo "=== Building wxWidgets ==="
 emmake make -j$(nproc 2>/dev/null || sysctl -n hw.ncpu)
 
+# Create library symlinks (remove -emscripten suffix for CMake compatibility)
+echo ""
+echo "=== Creating library symlinks ==="
+cd "$BUILD_DIR/lib"
+for lib in *-emscripten.a; do
+    if [ -f "$lib" ]; then
+        newname="${lib/-emscripten/}"
+        ln -sf "$lib" "$newname"
+    fi
+done
+
+# Create stub libraries for components wx-config reports but we didn't build
+# KiCad doesn't use these directly
+echo "Creating stub libraries..."
+for stub in richtext webview; do
+    emar rcs "libwx_wasmunivu_${stub}-3.2.a"
+    ln -sf "libwx_wasmunivu_${stub}-3.2.a" "libwx_wasmunivu_${stub}-3.2-emscripten.a"
+done
+
+cd "$BUILD_DIR"
+
 echo ""
 echo "=== Build complete ==="
 ls -lh "$BUILD_DIR"/lib/*.a 2>/dev/null || echo "Libraries built in $BUILD_DIR/lib"