Add PI Closeout governance for final PI repository and GitHub hygiene review.
- TEAM token: OWNER
- Ownership classification: governance / workflow governance
- TEAM ownership result: PASS
- docs_build/dev/PROJECT_INSTRUCTIONS.md
- docs_build/dev/ProjectInstructions/addendums/multi_team.md
- docs_build/dev/reports/codex_changed_files.txt
- docs_build/dev/reports/codex_review.diff
- docs_build/dev/reports/PR_26172_OWNER_031-pi-closeout-governance.md
- docs_build/dev/reports/PR_26172_OWNER_031-pi-closeout-governance-manual-validation-notes.md
- docs_build/dev/reports/PR_26172_OWNER_031-pi-closeout-governance-instruction-compliance-checklist.md
- Added PI Closeout governance to require approved-work merge status, clean synchronized main, open PR review, branch review, active workstream review, deferred work list, and next PI queue recommendations.
- Added required PI closeout report fields.
- Preserved EOD Workstream Closeout as authoritative for final repository state.
- Prohibited PI closeout from implying approval to merge, close PRs, delete branches, or remove deferred work without explicit owner approval.
- git diff --check: PASS
- Verified PI Closeout governance exists: PASS
- Verified required PI closeout report fields exist: PASS
- Verified no conflicting governance wording: PASS
- Verified EOD closeout remains authoritative: PASS
- Playwright: skipped because this is docs/governance-only.
- Samples: skipped because no runtime, sample, or UI files changed.