MCP `confirm_wait`: a person says an issue may go ahead although what it waited for closed dropped or split #5003

Done: MCP confirm_wait { app, issue, blocker } confirms that issue may go ahead although blocker closed as dropped or split, through the same action the API uses (confirmIssue, POST …/issues/:number/dependencies/:blocker/confirm), so its rules, refusals and access are exactly the route's — no second implementation.

• [ ] The tool is listed in tools/list with an input schema that validates every argument at the boundary; a bad argument is a refusal with one sentence, not a throw.
• [ ] The answer is JSON with a says sentence, like the tools beside it.
• [ ] A row in docs/MCP.md's tool table.
• [ ] Tests: a writer succeeds, a reader, an agent or a stranger is refused as the route refuses them, and a bad argument is refused. The crew's own agents are refused (the crew may not unpark itself), and after a confirm the map tool no longer shows the issue parked on that blocker.

Files: src/http/mcp.ts, docs/MCP.md, one new test file. Risk: mcp.ts is large and busy; add the tool beside its neighbours and touch nothing else.