feat(worker): add PlanningMergeOrchestrator.AbortAsync

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

@@ -216,6 +216,35 @@ public sealed class PlanningMergeOrchestratorTests : IDisposable
         });
     }
 
+    [Fact]
+    public async Task AbortAsync_AfterConflict_RestoresCleanRepoAndClearsState()
+    {
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+
+        var (parentId, subA, subB, _) = await SeedPlanningThreeChildrenMiddleConflictsAsync(db, repo);
+
+        var (orch, spy) = BuildOrchestrator(db);
+        await orch.StartAsync(parentId, "main", CancellationToken.None);
+
+        await orch.AbortAsync(parentId, CancellationToken.None);
+
+        using var ctx = db.CreateContext();
+        // Planning stays in Planned — NOT flipped to Done.
+        Assert.Equal(TaskStatus.Planned, ctx.Tasks.Single(t => t.Id == parentId).Status);
+        // Earlier successful merge stays merged.
+        Assert.Equal(WorktreeState.Merged, ctx.Worktrees.Single(w => w.TaskId == subA).State);
+        // Conflicted subtask's worktree stays Active (abort doesn't flip it).
+        Assert.Equal(WorktreeState.Active, ctx.Worktrees.Single(w => w.TaskId == subB).State);
+
+        Assert.Contains(spy, c => c.Method == "PlanningMergeAborted" && (string)c.Args[0]! == parentId);
+
+        // Repo no longer mid-merge.
+        var git = new GitService();
+        Assert.False(await git.IsMidMergeAsync(repo.RepoDir, CancellationToken.None));
+    }
+
     private (PlanningMergeOrchestrator orch, List<(string Method, object?[] Args)> calls) BuildOrchestrator(DbFixture db)
     {
         var fakeHub = new OrchestratorFakeHubContext();