Add Testing MCP Apps guide

Document how to test MCP Apps using `basic-host` and MCP Apps-compatible
hosts like Claude.ai and VS Code Copilot. Cover debugging features for
`basic-host`, and using `cloudflared` to expose local servers for remote
hosts.

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

typedoc.config.mjs

@@ -11,6 +11,7 @@ const config = {
     "docs/overview.md",
     "docs/quickstart.md",
     "docs/agent-skills.md",
+    "docs/testing-mcp-apps.md",
     "docs/patterns.md",
     "docs/migrate_from_openai_apps.md",
   ],