/review lands features on dev — and can promote dev to main

Signing off a plan used to archive it and leave the branch for later. Now Approve is the integrate step.

/review Approve still runs the AI critic and human survey. What changed is the finish:

1. Merge feature/<slug> into the integration branch (dev, else develop; create dev from mainline if needed).
2. Only then move the plan review-needed/ → completed/.
3. On merge conflict: abort, leave the plan in review-needed/, report the files — no silent partial land.

When the queue is empty and dev is ahead of main, bare /review (or /review --promote) runs a promotion review: log + shortstat for main..dev, optional AI pass, survey Promote to main / Skip. Promote merges integration into mainline. One decision per invocation — plan Approve never auto-chains into promotion.

Guards stay tight: survey is the only merge authorization, never force-push, push to origin only with confirm or --push after local success. /work still never merges; executors commit on the feature branch and finish to review-needed/ as before.

scripts/pending_merges.py remains the advisory safety net for branches that somehow never landed.