Add skeleton docs/patterns.md with type-checked companion file

Introduces a patterns documentation page for common MCP Apps recipes.
The skeleton includes TODO sections for: perceived latency, iframe/MCP Apps
coexistence, authenticated calls, private tools, theme changes, fullscreen,
host styling, data persistence, OpenAI migration, and error handling.

- Add `docs/patterns.md` to `projectDocuments` in `typedoc.config.mjs`
- Add `docs/patterns.ts` companion file with region-delimited code stubs
- Include `docs/**/*.ts` in `tsconfig.json` for type-checking
- Document the standalone docs pattern in `CLAUDE.md`

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

AGENTS.md

@@ -82,6 +82,8 @@ Guest UI (App) <--PostMessageTransport--> Host (AppBridge) <--MCP Client--> MCP
 
 JSDoc `@example` tags use `{@includeCode ./file.examples.ts#regionName}` to pull in type-checked code from companion `.examples.ts`/`.examples.tsx` files. Regions are marked with `//#region name` and `//#endregion name`, wrapped in functions (whose parameters provide types for external values). Region names follow `exportedName_variant` or `ClassName_methodName_variant` pattern (e.g., `useApp_basicUsage`, `App_hostCapabilities_checkAfterConnection`).
 
+Standalone docs in `docs/` (listed in `typedoc.config.mjs` `projectDocuments`) can also have type-checked companion `.ts` files using the same `@includeCode` pattern.
+
 ## Full Examples
 
 Uses npm workspaces. Full examples in `examples/` are separate packages: