Approve & Merge is disabled until the pending changes have been inspected:
DetailsIslandViewModel tracks ReviewDiffViewed (reset on task switch and on
every state change), MergeSectionViewModel raises DiffViewed when a diff or
combined diff is opened and exposes HasReviewableDiff, and a hint sits next
to the button. A review with nothing to inspect (sandbox run, no worktree)
approves straight through.
ClaudeDo-Task: f9809a93