feat(ui): wire batch selection, target loading and resolve seam

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

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

@@ -114,4 +114,54 @@ public class WorktreesOverviewBatchMergeTests
         Assert.False(called);
         Assert.Equal(BatchMergeOutcome.None, a.MergeOutcome);
     }
+
+    [Fact]
+    public void SelectedCount_tracks_checked_active_rows()
+    {
+        var vm = NewVm();
+        var a = ActiveRow("a");
+        var b = ActiveRow("b");
+        var merged = ActiveRow("c"); merged.State = WorktreeState.Merged;
+        vm.AddRowForTest(a); vm.AddRowForTest(b); vm.AddRowForTest(merged);
+
+        Assert.Equal(0, vm.SelectedCount);
+        a.IsChecked = true;
+        Assert.Equal(1, vm.SelectedCount);
+        b.IsChecked = true;
+        merged.IsChecked = true;
+        Assert.Equal(2, vm.SelectedCount);
+        a.IsChecked = false;
+        Assert.Equal(1, vm.SelectedCount);
+    }
+
+    [Fact]
+    public void ResolveConflict_invokes_seam_with_task_and_target()
+    {
+        var vm = NewVm();
+        vm.SelectedTarget = "release";
+        var row = ActiveRow("x"); row.MergeOutcome = BatchMergeOutcome.Conflict;
+
+        (string Task, string Target)? captured = null;
+        vm.RequestConflictResolution = (taskId, target) => { captured = (taskId, target); return System.Threading.Tasks.Task.CompletedTask; };
+
+        vm.ResolveConflictCommand.Execute(row);
+
+        Assert.Equal(("x", "release"), captured);
+    }
+
+    [Fact]
+    public void MergeAll_canExecute_requires_target_selection_and_idle()
+    {
+        var vm = NewVm();
+        var a = ActiveRow("a");
+        vm.AddRowForTest(a);
+
+        Assert.False(vm.MergeAllCommand.CanExecute(null));
+        a.IsChecked = true;
+        Assert.False(vm.MergeAllCommand.CanExecute(null));
+        vm.SelectedTarget = "main";
+        Assert.True(vm.MergeAllCommand.CanExecute(null));
+        vm.IsMerging = true;
+        Assert.False(vm.MergeAllCommand.CanExecute(null));
+    }
 }