MCP action tools: await_request, save_as_test, copy_as_curl, clear_requests

[doganarif]

Completes the agent workflow around #58:

• await_request blocks (default 30s, max 120s) until a request matching method/path/status filters is captured, then returns it in full. An agent can trigger a flow itself — curl, a test, a browser tool — and catch exactly what happened. Uses the store's notification hub when available with a 200ms polling fallback.
• save_as_test renders a captured request as a runnable Go httptest regression test asserting the captured status.
• copy_as_curl renders a capture as a shell-quoted curl command.
• clear_requests empties the store for a clean repro.

Wrap now skips re-wrapping stores that already notify, so the pattern of sharing one store.WithNotify(...) between Wrap and the MCP handler gives await_request push latency instead of polling.