A builder whose issue names an MCP tool file is told to run test/mcp-size.test.ts before pushing, and to extend an existing tool rather than add one #6440

Flow work for #6217 and #5994. Nine pulls went red on the shared tools/list budget, and #2927 was parked on it twice. Each builder learned the budget only from the check, after spending a full run.

Done when:

• [ ] When the issue's title or body names a path under src/http/mcp/ or the word "MCP", the task text in src/crew/brief.ts adds two sentences. (1) Run bun test test/mcp-size.test.ts before pushing; it names the five costliest tools when it fails. (2) Prefer an action or kind on an existing tool (docs/MCP.md, "Room for a new tool"), and never raise the ceilings.
• [ ] Briefs for other issues are unchanged, byte for byte.
• [ ] A test builds the brief for an MCP issue and for a plain issue, and checks that the lines are present in one and absent from the other.

Files: src/crew/brief.ts, its test (test/crew-brief*.test.ts or a new test/brief-mcp-size.test.ts).