feat(ui): wire worktree overview modal entry points

Add list context-menu command (per-list mode) and Help menu entry (global mode) for the WorktreesOverviewModal; register VM and factory in DI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.App/Program.cs

@@ -95,6 +95,8 @@ sealed class Program
 
         // ViewModels
         sc.AddTransient<WorktreeModalViewModel>();
+        sc.AddTransient<WorktreesOverviewModalViewModel>();
+        sc.AddTransient<Func<WorktreesOverviewModalViewModel>>(sp => () => sp.GetRequiredService<WorktreesOverviewModalViewModel>());
         sc.AddSingleton<IPrimeScheduleApi, WorkerPrimeScheduleApi>();
         sc.AddTransient<PrimeClaudeTabViewModel>();
         sc.AddTransient<SettingsModalViewModel>();