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/MergeModalViewModelTests.cs

@@ -26,6 +26,9 @@ public class MergeModalViewModelTests
         /// Result for a call with autostash=false; the autostash retry always merges.
         public MergeResultDto CleanResult { get; set; } = new("merged", new List<string>(), null);
 
+        /// Result for the autostash retry.
+        public MergeResultDto StashedResult { get; set; } = new("merged", new List<string>(), null);
+
         public override Task<MergeTargetsDto?> GetMergeTargetsAsync(string taskId) =>
             Task.FromResult(Targets);
 
@@ -36,7 +39,7 @@ public class MergeModalViewModelTests
             CapturedAutostash = autostash;
             return BlockMerge
                 ? MergeGate.Task
-                : Task.FromResult(autostash ? new MergeResultDto("merged", new List<string>(), null) : CleanResult);
+                : Task.FromResult(autostash ? StashedResult : CleanResult);
         }
     }
 
@@ -189,4 +192,26 @@ public class MergeModalViewModelTests
 
         Assert.Null(vm.ProgressMessage);
     }
+
+    [Fact]
+    public async Task Stash_retry_ending_in_conflict_hands_the_stash_consent_to_the_resolver()
+    {
+        // Regression: the resolver restarts the merge itself and needs the same consent, or the
+        // dirty target refuses it and the resolver never opens.
+        var worker = new Worker
+        {
+            CleanResult = new("dirty_target", new List<string>(), "uncommitted changes"),
+            StashedResult = new("conflict", new List<string> { "a.cs" }, null),
+        };
+        bool? capturedAutostash = null;
+        var vm = new MergeModalViewModel(worker, new MergeCoordinator
+        {
+            Handler = (_, _, autostash) => { capturedAutostash = autostash; return Task.CompletedTask; },
+        });
+        await vm.InitializeAsync("task-1", "do the thing");
+
+        await vm.StashAndMergeCommand.ExecuteAsync(null);
+
+        Assert.True(capturedAutostash);
+    }
 }