Grow the detail-pane Git tab into the review+merge cockpit: target,
pre-flight mergeability, inspect actions, then the four review verbs
(Approve & Merge / Send back / Park / Cancel) plus a demoted
Reset (discard branch).
The decision block is gated independently of the merge controls so
sandbox (no-worktree) review tasks still get the buttons.
- Add ParkReviewCommand (-> RejectReviewToIdleAsync)
- Send back (reject-to-queue) disabled until feedback is entered
- Remove the mislabeled [Continue]/[Reset] line from the Output tab
- Accent dot on the Git tab while awaiting review
