[shiplog/plan] Backfill Last-code-by on existing open PRs

[devallibus]

Context

Once the Last-code-by: field is defined (see companion issue), existing open PRs need the field added to their bodies so the identity-aware hunt command can read it without falling back to git commit forensics. This is a one-time housekeeping task.

Design Summary

• Audit each open PR to determine who made the last code changes (via git log on the PR branch)
• Add Last-code-by: to each PR body as an in-place edit with Updated-by: provenance

Approach

For each open PR: inspect git log on the PR branch to identify the model that authored the most recent commits, then edit the PR body via gh pr edit to add Last-code-by: and an Updated-by: provenance footer.

Tasks

• T1: Audit and backfill open PRs [tier-3]
  • What: For each open PR at time of execution, run gh pr view <N> --json headRefName to get the branch, then inspect the branch's commit history to identify the last code author model. Edit each PR body via gh pr edit <N> --body-file to add Last-code-by: field and an Updated-by: provenance footer per signing conventions
  • Files: No file changes — GitHub API operations only
  • Allowed to change: PR bodies on GitHub (add field, do not remove existing content)
  • Must not change: Any repository files
  • Verification: gh pr view <N> --json body shows Last-code-by: field for each updated PR
  • Return artifact: List of PRs updated with the field value added to each
  • Decision budget: none
  • Accept when: All open PRs have Last-code-by: in their body

Open Questions

• None — this is a mechanical backfill once the field definition exists

---

Authored-by: claude/opus-4.6 (claude-code)
Captain's log entry created by shiplog

[devallibus]

Dependencies

• Blocked by [shiplog/plan] Add Last-code-by provenance field and update review-gating rules #123 — Last-code-by: field must be defined before backfilling
• Unblocks [shiplog/plan] Identity-aware hunt command with review-gating and tier filtering #122 — Identity-aware hunt command works better with backfilled field (but has git fallback)

Authored-by: claude/opus-4.6 (claude-code)