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>

docs/patterns.md

@@ -0,0 +1,69 @@
+---
+title: Patterns
+---
+
+# MCP Apps Patterns
+
+This document covers common patterns and recipes for building MCP Apps.
+
+## [TODO] Tools that are private to Apps
+
+Use `Tool._meta.ui.visibility: ["apps"]` to make tools only visible to Apps.
+
+{@includeCode ./patterns.ts#privateTools}
+
+## [TODO] Authenticated calls from App
+
+- Use tool calls / read resources
+  - See [PDF example](https://github.com/modelcontextprotocol/ext-apps/blob/main/examples/pdf-viewer) to read binaries by chunks to avoid call tool size limitations on platforms like claude.ai
+- Pass auth token in `_meta` (will be loaded again in the future) + refresh token + store in local storage (see Persist data section below)
+
+{@includeCode ./patterns.ts#authenticatedCalls}
+
+## [TODO] Giving errors back to model
+
+- Before app runs: validate inputs in tool call
+- After it runs: use `updateModelContext`
+
+{@includeCode ./patterns.ts#errorsToModel}
+
+## [TODO] Support native host styling / use CSS variables
+
+{@includeCode ./patterns.ts#hostStyling}
+
+## [TODO] Reacting to light/dark theme changes
+
+{@includeCode ./patterns.ts#lightDarkTheme}
+
+## [TODO] Support fullscreen / exit fullscreen
+
+{@includeCode ./patterns.ts#fullscreen}
+
+## [TODO] Persist data (incl. widget state)
+
+- Note: OAI's `window.openai.setWidgetState({modelContent, privateContent, imageIds})` has only a partial equivalent in the MCP Apps spec (for now!): `App.updateModelContext({content, structuredContent})`
+- For data persistence / to reload when conversation is reloaded, you must use localStorage / IndexedDb with `hostInfo.toolInfo.id` as key returned `CallToolResult._meta.widgetUUID = randomUUID()`
+
+{@includeCode ./patterns.ts#persistData}
+
+## [TODO] Lower perceived latency / manage loading time
+
+Leverage partial inputs to show widgets as possible.
+
+Beware of partial JSON being partial (but healed), so some of your objects may not be complete (e.g. in a list you may need to skip the last item if your code validates input schemas strictly).
+
+{@includeCode ./patterns.ts#lowerPerceivedLatency}
+
+## [TODO] Supporting both iframe & MCP Apps in same binary
+
+See recipe: https://github.com/modelcontextprotocol/ext-apps/issues/34
+
+{@includeCode ./patterns.ts#iframeAndMcpApps}
+
+## [TODO] Migrating from OpenAI to MCP Apps
+
+See [OpenAI -> MCP Apps](https://docs.google.com/document/d/13ROImOR9B8xc32yhqsFyC9Hh3_H63JFORDIyjyIPcU4/edit) migration guide.
+
+Also: [Managing State](https://platform.openai.com/docs/actions/managing-state) (OpenAI)
+
+{@includeCode ./patterns.ts#migrateFromOpenai}