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>

src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs

@@ -209,12 +209,13 @@ public sealed class PlanningSessionManager
             throw new InvalidOperationException(
                 finalizeResult.Reason ?? $"Could not finalize planning for task {taskId}.");
 
-        int count = 0;
+        // Establish the blocked-by chain but leave children Idle; queueing is a
+        // deliberate user action ("Queue plan"), never an automatic finalize step.
+        // queueAgentTasks is accepted for compatibility but no longer auto-queues.
         var children = await tasks.GetChildrenAsync(taskId, ct);
-        if (queueAgentTasks && children.Count > 0)
-            count = await _chain.SetupChainAsync(taskId, ct);
-        else
-            count = children.Count;
+        int count = children.Count;
+        if (children.Count > 0)
+            count = await _chain.SetupChainAsync(taskId, enqueue: false, ct);
 
         // Best-effort cleanup — don't block finalization on git state.
         await TryCleanupWorktreeAsync(taskId, lists, settings, ct);