feat: migrate docs to Fumadocs framework

- Auto-generated sidebar from file structure
- Built-in search and TOC
- MDX native support with frontmatter
- Removed hand-written Sidebar component
- Docs now at /docs/* route (Landing/Blocks/Create/Examples unchanged)
- Content in content/docs/ as MDX files

packages/docs/tsconfig.json

@@ -5,12 +5,13 @@
     "allowJs": true,
     "noEmit": true,
     "incremental": true,
-    "moduleResolution": "node",
+    "moduleResolution": "bundler",
     "resolveJsonModule": true,
     "isolatedModules": true,
     "jsx": "preserve",
     "paths": {
-      "@/*": ["./*"]
+      "@/*": ["./*"],
+      "@/.source": ["./.source/index.ts"]
     },
     "plugins": [
       {