feat(claude-do): merge feat(ui): "Worktree öffnen" im Kontextmenü der Task-Zeile

ClaudeDo-Task: 9be17e29e0b54f42ba9385b0cebe89d5

tests/ClaudeDo.Worker.Tests/UiVm/TaskRowViewModelTests.cs

@@ -64,6 +64,60 @@ public class TaskRowViewModelTests
         Assert.Contains(nameof(TaskRowViewModel.ShowNumberBadge), raised);
     }
 
+    [Fact]
+    public void CanOpenWorktree_True_And_ReasonNull_When_Path_Present()
+    {
+        var vm = new TaskRowViewModel { Id = "t" };
+        vm.WorktreePath = @"C:\repo\worktrees\t";
+
+        Assert.True(vm.CanOpenWorktree);
+        Assert.Null(vm.OpenWorktreeDisabledReason);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    public void CanOpenWorktree_False_And_ReasonSet_When_Path_Missing(string? path)
+    {
+        var vm = new TaskRowViewModel { Id = "t" };
+        vm.WorktreePath = path;
+
+        Assert.False(vm.CanOpenWorktree);
+        Assert.NotNull(vm.OpenWorktreeDisabledReason);
+    }
+
+    [Fact]
+    public void OpenWorktreeGate_Raises_PropertyChanged_On_WorktreePath_Change()
+    {
+        var vm = new TaskRowViewModel { Id = "t" };
+        var raised = new List<string?>();
+        vm.PropertyChanged += (_, e) => raised.Add(e.PropertyName);
+
+        vm.WorktreePath = @"C:\repo\worktrees\t";
+
+        Assert.Contains(nameof(TaskRowViewModel.CanOpenWorktree), raised);
+        Assert.Contains(nameof(TaskRowViewModel.OpenWorktreeDisabledReason), raised);
+    }
+
+    [Fact]
+    public void WorktreePath_SetFromEntity_MapsFromWorktreePath()
+    {
+        var entity = new TaskEntity
+        {
+            Id = "t", ListId = "l1", Title = "Task", CreatedAt = DateTime.UtcNow,
+            Worktree = new WorktreeEntity
+            {
+                TaskId = "t", Path = @"C:\repo\worktrees\t", BranchName = "b",
+                BaseCommit = "abc123", CreatedAt = DateTime.UtcNow,
+            },
+        };
+        var vm = TaskRowViewModel.FromEntity(entity);
+
+        Assert.Equal(@"C:\repo\worktrees\t", vm.WorktreePath);
+        Assert.True(vm.CanOpenWorktree);
+    }
+
     [Fact]
     public void IsDropTarget_Follows_Either_DropHint_And_Raises_PropertyChanged()
     {