feat(ui): richer diff viewer + surface child roadblocks on parents

- UnifiedDiffParser detects added/deleted/renamed/binary files; diff
  modal shows a file list, binary/empty placeholders, and can diff a
  merged task by commit range after its worktree is gone
- DetailsIslandViewModel flags children needing attention (failed,
  cancelled, awaiting review, or with roadblocks) on the parent
- GitService gains worktree head-commit/range support; planning chain,
  merge orchestration, and session manager tweaks with updated tests
- refresh app/installer/worker icons

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -121,19 +121,20 @@ public sealed class PlanningEndToEndTests : IDisposable
         Assert.Equal(PlanningPhase.Finalized, reload!.PlanningPhase);
 
         var kids = await _tasks.GetChildrenAsync(parent.Id);
-        // SetupChainAsync auto-attaches agent tag and queues all children;
-        // the first one is unblocked, the rest are BlockedBy their predecessor.
-        Assert.Equal(TaskStatus.Queued, kids[0].Status);
+        // Finalize no longer auto-queues. Children stay Idle and chain-linked
+        // (head unblocked, rest BlockedBy their predecessor) until the user
+        // explicitly queues the plan.
+        Assert.Equal(TaskStatus.Idle, kids[0].Status);
         Assert.Null(kids[0].BlockedByTaskId);
-        Assert.Equal(TaskStatus.Queued, kids[1].Status);
+        Assert.Equal(TaskStatus.Idle, kids[1].Status);
         Assert.Equal(kids[0].Id, kids[1].BlockedByTaskId);
     }
 
-    // Regression: original bug was "queue never picks up planning tasks". After Finalize
-    // with queueAgentTasks=true, the first child must be claimable by the queue picker
-    // automatically — without anyone calling WakeQueue() manually.
+    // Regression: original bug was "queue never picks up planning tasks". Finalize
+    // leaves children Idle; queueing the plan (the explicit user gate) must make the
+    // first child claimable by the picker automatically — without a manual WakeQueue().
     [Fact]
-    public async Task FinalizeAsync_FirstChildIsClaimedByPicker_WithinDeadline()
+    public async Task QueuePlanAfterFinalize_FirstChildIsClaimedByPicker_WithinDeadline()
     {
         var listId = Guid.NewGuid().ToString();
         var wd = Path.Combine(Path.GetTempPath(), $"cd_e2e_wd_{Guid.NewGuid():N}");
@@ -160,12 +161,18 @@ public sealed class PlanningEndToEndTests : IDisposable
 
         var kidsBefore = await _tasks.GetChildrenAsync(parent.Id);
         var firstChildId = kidsBefore[0].Id;
-        var wakesBefore = _built.WakeCount();
 
         await _manager.FinalizeAsync(parent.Id, queueAgentTasks: true, CancellationToken.None);
 
-        // The picker should pick the first child immediately. Auto-wake fires inside
-        // _state.EnqueueAsync; we don't need a manual WakeQueue() for the bug to be fixed.
+        // Finalize leaves every child Idle — nothing is claimable yet.
+        var afterFinalize = await _tasks.GetChildrenAsync(parent.Id);
+        Assert.All(afterFinalize, k => Assert.Equal(TaskStatus.Idle, k.Status));
+
+        // Queueing the plan is the gate that enqueues + auto-wakes. The picker should
+        // then pick the first child immediately, without a manual WakeQueue().
+        var wakesBefore = _built.WakeCount();
+        await _built.Chain.QueuePlanAsync(parent.Id, CancellationToken.None);
+
         var picker = new QueuePicker(_db.CreateFactory());
 
         TaskEntity? claimed = null;
@@ -181,6 +188,6 @@ public sealed class PlanningEndToEndTests : IDisposable
         Assert.Equal(firstChildId, claimed!.Id);
         Assert.Equal(TaskStatus.Running, claimed.Status);
         Assert.True(_built.WakeCount() > wakesBefore,
-            "TaskStateService.EnqueueAsync should auto-wake the queue.");
+            "QueuePlanAsync → EnqueueAsync should auto-wake the queue.");
     }
 }