Implement wxClipboard and add button finder utility for canvas testing

wxClipboard:
- Update wxwidgets submodule with full wxClipboard implementation
- Add clipboard async functions to ASYNCIFY_IMPORTS in Makefile.wasm
- Update clipboard tests with correct button positions
- Add clipboard permissions to playwright config
- Update WHATWORKS.md to mark wxClipboard as working

Button Finder Utility:
- Add parametric button-finder.spec.ts for scanning canvas apps
- Utility scans for clickable buttons by detecting console log responses
- Excluded from regular test runs via testIgnore
- Supports APP_URL, START_Y, END_Y, STEP environment variables
- Document usage in tests/README.md

All 91 tests pass.

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

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

tests/playwright.config.ts

@@ -9,9 +9,14 @@ export default defineConfig({
   reporter: 'html',
   timeout: 60000,  // WASM can be slow to load
 
+  // Exclude button-finder from regular test runs - it's a utility, not a test
+  testIgnore: ['**/button-finder.spec.ts'],
+
   use: {
     baseURL: 'http://localhost:8080',
     trace: 'on-first-retry',
+    // Grant clipboard permissions for clipboard tests
+    permissions: ['clipboard-read', 'clipboard-write'],
   },
 
   projects: [