Add KiCad PCBnew WASM test infrastructure

- Add pcbnew-load.spec.ts: Tests for WASM runtime initialization
- Add pcbnew.html: Test harness for loading KiCad in browser
- Add setup-kicad-wasm.sh: Script to copy WASM from Docker build
- Add serve.json: COOP/COEP headers for SharedArrayBuffer support
- Update package.json: Add npm run test:kicad and setup:kicad scripts
- Update .gitignore: Exclude generated WASM/JS files from kicad/

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

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

tests/serve.json

@@ -0,0 +1,11 @@
+{
+  "headers": [
+    {
+      "source": "**/*",
+      "headers": [
+        { "key": "Cross-Origin-Opener-Policy", "value": "same-origin" },
+        { "key": "Cross-Origin-Embedder-Policy", "value": "require-corp" }
+      ]
+    }
+  ]
+}