After a merge lands on the target branch, TaskMergeService now rebases every
other WaitingForReview task's active worktree onto the new tip -- but only
when that branch actually touches a file the merge just changed, computed via
GitService.GetChangedFileNamesAsync (both the merge's landed files and each
candidate's own diff). A branch merely behind is left alone. On conflict or
any other failure the rebase is aborted and the branch is left exactly as it
was, with a WorkerLog warning naming the task; a successful rebase updates the
worktree's recorded BaseCommit/HeadCommit and broadcasts WorktreeUpdated.
mika kuns
2662e7bd98