Include OAI migration guide in TypeDoc documentation

- Add migration guide to `projectDocuments` in `typedoc.config.mjs`
- Add YAML frontmatter with title to `migrate_from_openai_apps.md`
- Fix heading hierarchy (### → ####) for proper nesting
- Fix "Client-side" → "Client-Side" capitalization
- Rename "Full Migration Example" → "Client-Side Migration Example"
- Remove TODO placeholder sections from `patterns.md`

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

typedoc.config.mjs

@@ -4,7 +4,11 @@ import { OptionDefaults } from "typedoc";
 const config = {
   blockTags: [...OptionDefaults.blockTags, "@description"],
   intentionallyNotExported: ["AppOptions"],
-  projectDocuments: ["docs/quickstart.md", "docs/patterns.md"],
+  projectDocuments: [
+    "docs/quickstart.md",
+    "docs/patterns.md",
+    "docs/migrate_from_openai_apps.md",
+  ],
   entryPoints: [
     "src/server/index.ts",
     "src/app.ts",