fix(merge): pass the stash consent to the conflict resolver so it opens on a dirty target

The resolver restarts the merge via StartConflictMerge, which had no autostash.
After a stash-retry approve reported 'conflict', the restart hit the same dirty
target, got 'dirty_target' and the resolver silently never opened. Thread the
consent through the hub, client, coordinator and resolver; surface a refusal in
the footer instead of dropping it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

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

@@ -30,9 +30,14 @@ public class ConflictResolverViewModelTests
         public string? ContinuedPlanningParent;
         public string? AbortedPlanningParent;
 
-        public override Task<MergeResultDto> StartConflictMergeAsync(string taskId, string targetBranch)
+        /// <summary>Models a target working tree with uncommitted changes: refused unless the caller consented to the stash.</summary>
+        public bool DirtyTarget;
+
+        public override Task<MergeResultDto> StartConflictMergeAsync(string taskId, string targetBranch, bool autostash = false)
         {
             StartCalled = true;
+            if (DirtyTarget && !autostash)
+                return Task.FromResult(new MergeResultDto("dirty_target", System.Array.Empty<string>(), "target working tree has uncommitted changes"));
             return Task.FromResult(new MergeResultDto("conflict", new[] { "README.md" }, null));
         }
 
@@ -63,6 +68,19 @@ public class ConflictResolverViewModelTests
         public override Task AbortConflictMergeAsync(string taskId) { Aborted = true; return Task.CompletedTask; }
     }
 
+    [Fact]
+    public async Task OpenAsync_DirtyTarget_OpensOnlyWithStashConsent()
+    {
+        // Regression: a dirty target refused the resolver's own merge restart, so it never opened.
+        var refused = new ConflictResolverViewModel(new FakeWorker { DirtyTarget = true }, "task-1");
+        Assert.False(await refused.OpenAsync("main"));
+        Assert.Equal("target working tree has uncommitted changes", refused.Error);
+
+        var consented = new ConflictResolverViewModel(new FakeWorker { DirtyTarget = true }, "task-1");
+        Assert.True(await consented.OpenAsync("main", autostash: true));
+        Assert.Null(consented.Error);
+    }
+
     [Fact]
     public async Task OpenAsync_LoadsConflicts_AndBlocksContinueUntilResolved()
     {