branchPullRequest confirms every merged or closed answer against fresh git
reads, bypassing the 5-minute git-state cache. The settlement and PR-sync
sweeps call it once a minute, so a thread whose branch PR is merged or closed
but stays unsettled spawned git processes every sweep.

Both sweeps now take the remembered answer (confirmTerminal: false) and
confirm only before they act: settlement rereads git state only when the
answer would settle a thread, and PR sync already rereads it before saving a
link. Other callers, including worktree cleanup, keep the default confirm.

Fixes #24098. Implementation from #24099.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>