Expose a skill over runx mcp serve and prove it from a client

Serve a runx skill over MCP (runx mcp serve <skill-ref...> [--http-listen [addr]]), drive it from a real MCP client, and report the manifest, the tools exposed, and a successful call with structured output. MCP docs: runx.ai/docs/mcp, runx.ai/integrations.

Deliverable:manifest.json (the served MCP manifest with the tool list), results.json (at least one real tool call with its structured response), and a report naming the client and the exact runx mcp serve command.