ci: CodeRabbit re-reviews every push and starves the review queue #3517

Problem

The CodeRabbit plan allows 1 included review per hour. reviews.auto_review.auto_incremental_review is unset in .coderabbit.yml, so it takes its schema default of true ("Re-run the review on each push"). Every push to any open PR therefore uses up the hour, including a push that fixes the previous review's findings and updates to older PRs.

Evidence, 2026-09-23 13:52–15:32 UTC: reviews went to #3497 (twice), #3483 and #3353, each triggered by a push. Over the same period the coderabbit-queue requests for #3500 got "Review limit reached" five times. With 14 open PRs, the queue cannot finish.

#3477 did not address this. base_branches: '.*' means more PRs are eligible for review.

Change

Set auto_incremental_review: false. A newly opened PR still gets its automatic first review. Re-reviews after fixes are requested explicitly with @coderabbitai review, which the queue does in merge order.