build: implement bundling system with Rollup

Phase 1-3 Complete:
- ✅ Installed Rollup with all required plugins
- ✅ Created rollup.config.js for UMD, ESM, CJS builds
- ✅ Created src/index.js entry point
- ✅ Created src/styles.css for CSS bundling
- ✅ Added ES6 exports to debug-system.js
- ✅ Excluded Node.js-only html-generator.js from bundle

Build outputs:
- dist/testdrive-jsui.js (217KB UMD)
- dist/testdrive-jsui.min.js (107KB minified!)
- dist/testdrive-jsui.esm.js (199KB ES Module)
- dist/testdrive-jsui.cjs.js (199KB CommonJS)
- dist/testdrive-jsui.css (minified, all styles inlined)

All builds include source maps for debugging.

js/core/debug-system.js

@@ -287,4 +287,7 @@ class MarkitectDebugSystem {
 }
 
 // Initialize and expose globally
-window.MarkitectDebugSystem = new MarkitectDebugSystem();
+window.MarkitectDebugSystem = new MarkitectDebugSystem();
+
+// ES6 export for bundler
+export { MarkitectDebugSystem };