Repository-limit and agent-not-here refusals live in one module, read by migrate, repos, apps and the fleet #5720

Replaces #5655 with the same done, started fresh from main. Both tries went red on errors that escaped unrelated test files: explore-rank (#5667) and pull-merge-box (the issue this waits for).

For: At the repository limit, or naming an agent not here reads the same from every door (page, API, MCP, terminal) because it is said from one place. Today each sentence below is typed out separately in src/actions/migrate.ts, src/actions/repos.ts, src/web/pages/apps.ts, src/fleet/verbs.ts, src/tui/screens/common.ts.

Done:

• [ ] src/actions/crew_limit_words.ts exports these sentences (new, or the module that already owns that concept; say which in the pull):

- "at the repositories limit" - "That agent is not on this forge." - "that agent is not on this repository's crew"

• [ ] Every file named imports them, and grep -rn for each sentence under src/ finds only the module.
• [ ] Pages, screens and answers are byte-for-byte unchanged: every existing test passes as it is.
• [ ] A new test/crew-limit-words.test.ts asserts each file named no longer contains the literal (read as text), and fails if a copy is typed back.
• [ ] Before pushing, run test/crew-limit-words.test.ts, the tests of the files you touched, bun x tsc --noEmit and, if src/web changed, bun scripts/design-lint.ts. A red test elsewhere that main also has is named in the pull, not a reason to stop.

Files: src/actions/crew_limit_words.ts, src/actions/migrate.ts, src/actions/repos.ts, src/web/pages/apps.ts, src/fleet/verbs.ts, src/tui/screens/common.ts, test/crew-limit-words.test.ts. Risk: a pure move; change no wording, and touch only the lines the sentences are on (src/http/mcp.ts and src/http/api.ts are edited in parallel).