docs(squad): close #631 incident response — revert, CI guards, git safety rules

Incident #631 complete closure:
- Surgeon reverted problematic commit 1ab2f5c on dev (restored 361 files)
- Booster added CI deletion guards & canary checks to squad-ci.yml
- RETRO documented Git Safety mandatory rules in copilot-instructions.md
- PRs created and ready for merge (squad/631-ci-deletion-guard, squad/631-copilot-git-safety)
- Issue #631 closed with incident summary

Team memory updated:
- Orchestration log: 2026-03-26T17-28-631-closure.md
- Session log: 2026-03-26T17-28-631-closure.md

Incident response: Full parallel execution by Surgeon, Booster, RETRO agents.
Resolution: EMU auth restrictions resolved, manual coordination by Coordinator.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
