feat(ui): Mission Control Recent Sessions mit verschachtelten Handoffs

Neue Tabelle mission_control_sessions (Migration AddMissionControlSessions), befuellt vom
InteractiveLaunchSpecService bei Task-, Ad-hoc- und Handoff-Kacheln. Flyout im Mission-Control-Header
listet die letzten 14 Tage / 50 Sessions, Handoffs eingerueckt unter ihrer Ursprungs-Session, mit
Fortsetzen (--resume im gespeicherten cwd) und Brief anzeigen.

tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs

@@ -130,6 +130,8 @@ public abstract class StubWorkerClient : IWorkerClient
         => Task.FromResult(new LaunchSpec(directory, "claude", Array.Empty<string>(), new Dictionary<string, string>()));
     public virtual Task<LaunchSpec> GetSessionHandoffLaunchSpecAsync(string paneId, string cwd, string briefPath, string? taskId, CancellationToken ct = default)
         => Task.FromResult(new LaunchSpec(cwd, "claude", Array.Empty<string>(), new Dictionary<string, string>()));
+    public virtual Task<LaunchSpec> GetResumeSessionLaunchSpecAsync(string sessionId, string paneId, CancellationToken ct = default)
+        => Task.FromResult(new LaunchSpec(".", "claude", Array.Empty<string>(), new Dictionary<string, string>()));
     public virtual Task<LaunchSpec> GetMergeHelperLaunchSpecAsync(IReadOnlyList<string> taskIds, string listId, string handlerTaskId, string? model = null, CancellationToken ct = default)
         => Task.FromResult(new LaunchSpec(".", "claude", Array.Empty<string>(), new Dictionary<string, string>()));
     public virtual Task<string> CreateMergeHelperTaskAsync(

tests/ClaudeDo.Ui.Tests/ViewModels/MissionControlViewModelTests.cs

@@ -42,6 +42,23 @@ public class MissionControlViewModelTests : IDisposable
     private MissionControlViewModel BuildVm(StubWorkerClient worker)
         => new MissionControlViewModel(new TestDbFactory(NewContext), worker, new UsagePillViewModel(worker));
 
+    [Fact]
+    public void RecentSessions_NestHandoffs_PutsIndirectHandoffsUnderTheirOrigin()
+    {
+        var t0 = new DateTime(2026, 9, 28, 8, 0, 0, DateTimeKind.Utc);
+        MissionControlSessionEntity S(string id, int minutes, string? from = null)
+            => new() { SessionId = id, Cwd = "c", Title = id, StartedAt = t0.AddMinutes(minutes), PredecessorSessionId = from };
+        // Newest first, as ListRecentAsync returns them. "orphan" names a predecessor outside the window.
+        var newestFirst = new[] { S("c", 40, "b"), S("other", 30), S("b", 20, "a"), S("orphan", 15, "gone"), S("a", 10) };
+
+        var rows = MissionControlViewModel.NestHandoffs(newestFirst)
+            .Select(r => (r.Session.SessionId, r.IsHandoff)).ToList();
+
+        Assert.Equal(
+            new[] { ("a", false), ("b", true), ("c", true), ("other", false), ("orphan", false) },
+            rows);
+    }
+
     // Gates the title/list-name DB lookup behind a manually-released TaskCompletionSource so two
     // overlapping Open*ConPtySessionAsync calls both run their synchronous dedupe-check prefix
     // to completion before either resumes past the DB await. This reproduces the open-path races

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

@@ -712,6 +712,43 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         Assert.Equal(ArgAfter(spec, "--session-id"), await ReadInteractiveSessionIdAsync(taskId));
     }
 
+    [Fact]
+    public async Task RecentSession_AdHocThenHandoff_RecordsChainAndResumesInCwd()
+    {
+        var paneId = NewPaneId();
+        var svc = BuildService();
+        var origin = ArgAfter(await svc.BuildForDirectoryAsync(_tempDir, paneId, CancellationToken.None), "--session-id");
+
+        var dir = Path.Combine(InteractiveLaunchSpecService.PaneSessionDir(paneId), "handoffs", "h1");
+        Directory.CreateDirectory(dir);
+        var briefPath = Path.Combine(dir, "brief.md");
+        File.WriteAllText(briefPath, $"Handed off from session `{origin}`.\n\nbrief");
+        var handoff = ArgAfter(await svc.BuildHandoffAsync(paneId, _tempDir, briefPath, null, CancellationToken.None), "--session-id");
+
+        using (var ctx = _db.CreateContext())
+        {
+            var repo = new MissionControlSessionRepository(ctx);
+            var first = await repo.GetAsync(origin);
+            var second = await repo.GetAsync(handoff);
+            Assert.NotNull(first);
+            Assert.Null(first!.PredecessorSessionId);
+            Assert.Equal(origin, second!.PredecessorSessionId);
+            Assert.Equal(first.Title, second.Title);
+            Assert.Equal(briefPath, second.BriefPath);
+        }
+
+        var resumePane = NewPaneId();
+        var resume = await svc.BuildResumeAsync(handoff, resumePane, CancellationToken.None);
+        Assert.Equal(_tempDir, resume.Cwd);
+        Assert.Equal(handoff, ArgAfter(resume, "--resume"));
+        AssertHandoffHint(resume, resumePane, handoff);
+    }
+
+    [Fact]
+    public async Task BuildResumeAsync_UnknownSession_ThrowsKeyNotFound()
+        => await Assert.ThrowsAsync<KeyNotFoundException>(
+            () => BuildService().BuildResumeAsync(Guid.NewGuid().ToString(), NewPaneId(), CancellationToken.None));
+
     [Fact]
     public async Task BuildHandoffAsync_BriefOutsidePaneDir_Throws()
     {