fix(worker): stage only resolved conflict paths in continue_merge

git add -A ran against the shared target checkout, sweeping in
whatever untracked or unrelated modified files a concurrent session
left there and committing them into an unrelated merge. Stage exactly
the paths that were reported conflicted and resolved instead.

src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs

@@ -315,7 +315,11 @@ public sealed class TaskMergeService
             if (stillConflicted.Count > 0)
                 return new MergeResult(StatusConflict, stillConflicted, "conflicts not fully resolved");
 
-            await _git.AddAllAsync(list.WorkingDir, ct);
+            // Stage exactly the resolved conflict paths — never `git add -A`, which would sweep
+            // untracked/unrelated changes left by other sessions into this merge commit (the
+            // target working dir is shared).
+            foreach (var path in unresolved)
+                await _git.AddPathAsync(list.WorkingDir, path, ct);
 
             var remaining = await _git.ListConflictedFilesAsync(list.WorkingDir, ct);
             if (remaining.Count > 0)

tests/ClaudeDo.Worker.Tests/Services/TaskMergeServiceTests.cs

@@ -447,6 +447,60 @@ public class TaskMergeServiceTests : IDisposable
         Assert.Equal(WorktreeState.Merged, wt.State);
     }
 
+    [Fact]
+    public async Task ContinueMergeAsync_UnrelatedChangesInSharedCheckout_AreNotStagedOrCommitted()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+
+        File.WriteAllText(Path.Combine(repo.RepoDir, "README.md"), "# main change\n");
+        File.WriteAllText(Path.Combine(repo.RepoDir, "tracked.txt"), "tracked v1\n");
+        GitRepoFixture.RunGit(repo.RepoDir, "add", "tracked.txt");
+        GitRepoFixture.RunGit(repo.RepoDir, "commit", "-am", "main change");
+
+        var wtPath = Path.Combine(Path.GetTempPath(), $"wt_{Guid.NewGuid():N}");
+        _wtCleanups.Add((repo.RepoDir, wtPath));
+        GitRepoFixture.RunGit(repo.RepoDir, "worktree", "add", "-b", "claudedo/t5", wtPath, repo.BaseCommit);
+        File.WriteAllText(Path.Combine(wtPath, "README.md"), "# branch change\n");
+        GitRepoFixture.RunGit(wtPath, "commit", "-am", "branch change");
+
+        var (_, task) = await SeedListAndTask(db, workingDir: repo.RepoDir, status: TaskStatus.Done);
+        await SeedWorktree(db, task.Id, wtPath, "claudedo/t5", repo.BaseCommit);
+
+        var (svc, _) = BuildService(db);
+
+        var first = await svc.MergeAsync(task.Id, "main", false, "msg",
+            leaveConflictsInTree: true, CancellationToken.None);
+        Assert.Equal(TaskMergeService.StatusConflict, first.Status);
+
+        // Simulate the user resolving the conflict.
+        File.WriteAllText(Path.Combine(repo.RepoDir, "README.md"), "# resolved\n");
+
+        // A concurrent session leaves stray changes in this shared checkout while the merge is
+        // paused — these must survive continue_merge untouched and never enter the merge commit.
+        File.WriteAllText(Path.Combine(repo.RepoDir, "untracked.txt"), "from another session\n");
+        File.WriteAllText(Path.Combine(repo.RepoDir, "tracked.txt"), "tracked v2 (unrelated edit)\n");
+
+        var result = await svc.ContinueMergeAsync(task.Id, CancellationToken.None);
+
+        Assert.Equal(TaskMergeService.StatusMerged, result.Status);
+
+        Assert.True(File.Exists(Path.Combine(repo.RepoDir, "untracked.txt")));
+        Assert.Equal("from another session\n", File.ReadAllText(Path.Combine(repo.RepoDir, "untracked.txt")));
+        Assert.Equal("tracked v2 (unrelated edit)\n", File.ReadAllText(Path.Combine(repo.RepoDir, "tracked.txt")));
+
+        var status = GitRepoFixture.RunGit(repo.RepoDir, "status", "--porcelain");
+        Assert.Contains("?? untracked.txt", status);
+        Assert.Contains(" M tracked.txt", status);
+
+        var committedFiles = GitRepoFixture.RunGit(repo.RepoDir, "show", "--name-only", "--pretty=format:", "HEAD");
+        Assert.DoesNotContain("untracked.txt", committedFiles);
+        Assert.DoesNotContain("tracked.txt", committedFiles);
+    }
+
     [Fact]
     public async Task ContinueMergeAsync_UnresolvedConflictMarkersLeft_RefusesAndDoesNotCommit()
     {