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.

rollup.config.js

@@ -0,0 +1,123 @@
+import resolve from '@rollup/plugin-node-resolve';
+import commonjs from '@rollup/plugin-commonjs';
+import babel from '@rollup/plugin-babel';
+import terser from '@rollup/plugin-terser';
+import postcss from 'rollup-plugin-postcss';
+import postcssImport from 'postcss-import';
+import autoprefixer from 'autoprefixer';
+import cssnano from 'cssnano';
+
+const production = !process.env.ROLLUP_WATCH;
+
+// Shared Babel config
+const babelConfig = {
+  babelHelpers: 'bundled',
+  exclude: 'node_modules/**',
+  presets: [
+    ['@babel/preset-env', {
+      targets: {
+        browsers: ['> 0.5%', 'last 2 versions', 'not dead']
+      }
+    }]
+  ]
+};
+
+// Shared plugins (without CSS)
+const getPluginsWithoutCSS = () => [
+  resolve({ browser: true }),
+  commonjs(),
+  babel(babelConfig),
+  // PostCSS but don't extract (CSS already extracted in first build)
+  postcss({
+    inject: false,  // Don't inject or extract, just process
+    extract: false
+  })
+];
+
+export default [
+  // UMD build (browser-friendly, default) - EXTRACTS CSS
+  {
+    input: 'src/index.js',
+    output: {
+      name: 'TestDriveJSUI',
+      file: 'dist/testdrive-jsui.js',
+      format: 'umd',
+      sourcemap: true,
+      exports: 'named',  // Fix mixing named/default exports warning
+      globals: {
+        marked: 'marked'
+      },
+      banner: `/*!
+ * TestDrive-JSUI v1.0.0
+ * JavaScript-first markdown editor library
+ * (c) 2025 MarkiTect Team
+ * Released under MIT License
+ */`
+    },
+    external: ['marked'], // Peer dependency
+    plugins: [
+      resolve({ browser: true }),
+      commonjs(),
+      babel(babelConfig),
+      postcss({
+        extract: 'testdrive-jsui.css',  // Extract CSS to separate file
+        minimize: production,
+        plugins: [
+          postcssImport(),  // Resolve @import statements first
+          autoprefixer(),
+          production && cssnano()
+        ].filter(Boolean),
+        sourceMap: true
+      })
+    ]
+  },
+
+  // UMD minified build
+  {
+    input: 'src/index.js',
+    output: {
+      name: 'TestDriveJSUI',
+      file: 'dist/testdrive-jsui.min.js',
+      format: 'umd',
+      sourcemap: true,
+      exports: 'named',
+      globals: {
+        marked: 'marked'
+      }
+    },
+    external: ['marked'],
+    plugins: [
+      ...getPluginsWithoutCSS(),
+      terser({
+        format: {
+          comments: /^!/
+        }
+      })
+    ]
+  },
+
+  // ESM build (for modern bundlers)
+  {
+    input: 'src/index.js',
+    output: {
+      file: 'dist/testdrive-jsui.esm.js',
+      format: 'esm',
+      sourcemap: true
+    },
+    external: ['marked'],
+    plugins: getPluginsWithoutCSS()
+  },
+
+  // CommonJS build (for Node.js)
+  {
+    input: 'src/index.js',
+    output: {
+      file: 'dist/testdrive-jsui.cjs.js',
+      format: 'cjs',
+      sourcemap: true,
+      exports: 'named'
+    },
+    external: ['marked'],
+    plugins: getPluginsWithoutCSS()
+  }
+];