Keeping the PR mergeable: merge the Base branch and conflict Repair #8

Parent

#2

What to build

Keeping the PR mergeable. After the PR is confirmed, thirdshift fetches and merges origin/<Base branch> into the Issue branch (merge, never rebase or force-push):

• A clean merge (or nothing to merge) is pushed.
• A conflicting merge is left in progress and handed to a conflict Repair session: the conflict Repair prompt from the spec, the same plugin and flags, logged to …-repair-1.jsonl. After the session, thirdshift pushes.

Acceptance criteria

• The Base branch advanced without conflict → merge commit pushed to the Issue branch; no Repair session
• The Base branch unchanged → no merge commit, no Repair
• A conflicting Base branch change → the fake claude is started with the conflict Repair prompt (Issue URL, PR URL, branch, and base filled in) while the merge is in progress; its resolution is pushed
• The Repair session log is …-repair-1.jsonl with the run's shared timestamp
• No rebase or force-push ever reaches origin

Blocked by

• Walking skeleton: a fresh run on the happy path #3