chore: move widget source into sidecar repo (widget-src/)

Widget builds from widget-src/ → public/widget.js
Vite outDir updated to ../public
.gitignore excludes node_modules

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

widget-src/vite.config.ts

@@ -0,0 +1,22 @@
+import { defineConfig } from 'vite';
+import preact from '@preact/preset-vite';
+
+export default defineConfig({
+    plugins: [preact()],
+    build: {
+        lib: {
+            entry: 'src/main.tsx',
+            name: 'HelixWidget',
+            fileName: () => 'widget.js',
+            formats: ['iife'],
+        },
+        outDir: '../public',
+        emptyOutDir: false,
+        minify: 'esbuild',
+        rollupOptions: {
+            output: {
+                inlineDynamicImports: true,
+            },
+        },
+    },
+});