fix(worker): clean up orphaned worktree when the DB row insert fails

If WorktreeAddAsync succeeds but the worktrees-row insert throws, the
worktree was left on disk and branch undeleted with nothing tracking it.
Wrap the insert in try/catch and best-effort remove the worktree+branch
(non-cancellable) before rethrowing.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/ClaudeDo.Worker.Tests/Runner/WorktreeManagerTests.cs

@@ -158,6 +158,37 @@ public class WorktreeManagerTests : IDisposable
         Assert.Null(row);
     }
 
+    [Fact]
+    public async Task CreateAsync_DbInsertFails_RemovesOrphanedWorktreeAndBranch()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var repo = CreateRepo();
+        var (task, list) = MakeEntities(repo.RepoDir);
+
+        // Seed the list but NOT the task: the worktrees-row insert references
+        // tasks(task_id) and fails the FK after `git worktree add` has succeeded.
+        var db = new DbFixture();
+        _dbFixtures.Add(db);
+        using (var seedCtx = db.CreateContext())
+            await new ListRepository(seedCtx).AddAsync(list);
+
+        var cfg = new WorkerConfig { WorktreeRootStrategy = "sibling" };
+        var mgr = new WorktreeManager(
+            new GitService(), db.CreateFactory(), cfg, NullLogger<WorktreeManager>.Instance);
+
+        await Assert.ThrowsAnyAsync<Exception>(
+            () => mgr.CreateAsync(task, list, CancellationToken.None));
+
+        var branchName = $"claudedo/{task.Id.Replace("-", "")}";
+        var branchList = GitRepoFixture.RunGit(repo.RepoDir, "branch", "--list", branchName);
+        Assert.True(string.IsNullOrWhiteSpace(branchList),
+            $"orphaned branch {branchName} should be cleaned up, got: {branchList}");
+
+        var worktreeList = GitRepoFixture.RunGit(repo.RepoDir, "worktree", "list");
+        Assert.DoesNotContain(task.Id, worktreeList);
+    }
+
     private static (TaskEntity task, ListEntity list) MakeEntities(string workingDir)
     {
         var listId = Guid.NewGuid().ToString();