feat(worker): add PlanningAggregator.BuildIntegrationBranchAsync

tests/ClaudeDo.Worker.Tests/Planning/PlanningAggregatorTests.cs

@@ -116,4 +116,99 @@ public class PlanningAggregatorTests : IDisposable
             CreatedAt = DateTime.UtcNow,
         });
     }
+
+    [Fact]
+    public async Task BuildIntegrationBranchAsync_NonConflictingChildren_ReturnsOkWithCombinedDiff()
+    {
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+        var (parentId, _, _) = await SeedPlanningWithTwoChildrenAsync(db, repo);
+
+        var git = new GitService();
+        var svc = new PlanningAggregator(db.CreateFactory(), git, NullLogger<PlanningAggregator>.Instance);
+
+        var result = await svc.BuildIntegrationBranchAsync(parentId, targetBranch: "main", CancellationToken.None);
+
+        var ok = Assert.IsType<CombinedDiffResult.Ok>(result);
+        Assert.EndsWith("-integration", ok.Value.IntegrationBranch);
+        Assert.Contains("diff --git", ok.Value.UnifiedDiff);
+
+        var branches = await git.ListLocalBranchesAsync(repo.RepoDir, CancellationToken.None);
+        Assert.Contains(branches, b => b == ok.Value.IntegrationBranch);
+    }
+
+    [Fact]
+    public async Task BuildIntegrationBranchAsync_ConflictingChildren_ReturnsFailedAndResetsBranch()
+    {
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+        var (parentId, subA, subB) = await SeedPlanningWithConflictingChildrenAsync(db, repo);
+
+        var git = new GitService();
+        var svc = new PlanningAggregator(db.CreateFactory(), git, NullLogger<PlanningAggregator>.Instance);
+
+        var result = await svc.BuildIntegrationBranchAsync(parentId, targetBranch: "main", CancellationToken.None);
+
+        var failed = Assert.IsType<CombinedDiffResult.Failed>(result);
+        Assert.Equal(subB, failed.Value.FirstConflictSubtaskId);
+        Assert.NotEmpty(failed.Value.ConflictedFiles);
+
+        Assert.False(await git.IsMidMergeAsync(repo.RepoDir, CancellationToken.None));
+    }
+
+    private async Task<(string parentId, string subA, string subB)> SeedPlanningWithConflictingChildrenAsync(
+        DbFixture db, GitRepoFixture repo)
+    {
+        using var ctx = db.CreateContext();
+        var listId = Guid.NewGuid().ToString();
+        ctx.Lists.Add(new ListEntity
+        {
+            Id = listId, Name = "test", CreatedAt = DateTime.UtcNow, WorkingDir = repo.RepoDir,
+        });
+        var parentId = Guid.NewGuid().ToString();
+        ctx.Tasks.Add(new TaskEntity
+        {
+            Id = parentId, ListId = listId, Title = "plan", CreatedAt = DateTime.UtcNow,
+            Status = TaskStatus.Planning, SortOrder = 0,
+        });
+        var subA = Guid.NewGuid().ToString();
+        var subB = Guid.NewGuid().ToString();
+        ctx.Tasks.Add(new TaskEntity
+        {
+            Id = subA, ListId = listId, Title = "A", CreatedAt = DateTime.UtcNow,
+            ParentTaskId = parentId, Status = TaskStatus.Done, SortOrder = 1,
+        });
+        ctx.Tasks.Add(new TaskEntity
+        {
+            Id = subB, ListId = listId, Title = "B", CreatedAt = DateTime.UtcNow,
+            ParentTaskId = parentId, Status = TaskStatus.Done, SortOrder = 2,
+        });
+        await ctx.SaveChangesAsync();
+
+        SeedWorktreeWithFile(ctx, repo, subA, "README.md", "A wins\n");
+        SeedWorktreeWithFile(ctx, repo, subB, "README.md", "B wins\n");
+        await ctx.SaveChangesAsync();
+
+        return (parentId, subA, subB);
+    }
+
+    private void SeedWorktreeWithFile(ClaudeDoDbContext ctx, GitRepoFixture repo, string taskId, string filename, string content)
+    {
+        var wtPath = Path.Combine(Path.GetTempPath(), $"wt_{Guid.NewGuid():N}");
+        _wtCleanups.Add((repo.RepoDir, wtPath));
+        var branch = $"claudedo/{taskId[..8]}";
+        GitRepoFixture.RunGit(repo.RepoDir, "worktree", "add", "-b", branch, wtPath, repo.BaseCommit);
+        File.WriteAllText(Path.Combine(wtPath, filename), content);
+        GitRepoFixture.RunGit(wtPath, "add", filename);
+        GitRepoFixture.RunGit(wtPath, "commit", "-m", $"edit {filename}");
+        var head = GitRepoFixture.RunGit(wtPath, "rev-parse", "HEAD").Trim();
+        ctx.Worktrees.Add(new WorktreeEntity
+        {
+            TaskId = taskId, Path = wtPath, BranchName = branch,
+            BaseCommit = repo.BaseCommit, HeadCommit = head,
+            DiffStat = null, State = WorktreeState.Active, CreatedAt = DateTime.UtcNow,
+        });
+    }
 }