fix(mcp): reject unsupported streams and close request resources #13793

GET /mcp opens an SSE stream on a stateless, per-request server with no producer to send messages or close it. Repeated client probes cause Cloudflare Workers to cancel hung requests and generate error logs.

• Reject non-POST methods with 405 and Allow: POST before loading the API spec or constructing MCP services.


• Return stateless JSON responses for POST requests and close each server in finally.


• Add Workers runtime regression coverage for SSE probes, resume headers, unsupported methods, JSON-RPC responses and errors, 50 concurrent reconnects, and a real SDK client.


• Install Wrangler locally and gate CI and staging/production release scripts on the runtime tests.

Validation on the master-based branch:
- pnpm test:chatgpt-app: 31 tests passed.
- pnpm test:mcp: clean Worker/API docs builds, 21 runtime tests passed, and deployment dry-run passed.
- JavaScript syntax checks and git diff --check passed.