feat(worker): auto-rebase overlapping WaitingForReview branches after a merge

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.

src/ClaudeDo.Data/Repositories/WorktreeRepository.cs

@@ -45,6 +45,17 @@ public sealed class WorktreeRepository
                 .SetProperty(w => w.MergeCommit, mergeCommit), ct);
     }
 
+    /// <summary>Records a successful auto-rebase: the branch's fork point moves to the rebased-onto
+    /// commit and its head moves to the new tip <c>git rebase</c> produced.</summary>
+    public async Task SetRebasedAsync(string taskId, string baseCommit, string headCommit, CancellationToken ct = default)
+    {
+        await _context.Worktrees
+            .Where(w => w.TaskId == taskId)
+            .ExecuteUpdateAsync(s => s
+                .SetProperty(w => w.BaseCommit, baseCommit)
+                .SetProperty(w => w.HeadCommit, headCommit), ct);
+    }
+
     public async Task DeleteAsync(string taskId, CancellationToken ct = default)
     {
         await _context.Worktrees.Where(w => w.TaskId == taskId).ExecuteDeleteAsync(ct);