fix(merge): unresolved conflicts compose to empty, not Ours (+ review nits)

Code-review follow-ups before push:
- MergeFile.ResultText/Compose() fell back to Ours for unresolved conflicts while
  the editor seeds them empty — align both on empty so the public model matches the
  pane and Continue can't silently auto-accept Ours.
- Bound the gutter re-layout retry (was an unbounded Background re-post when the
  editor isn't laid out, e.g. minimized).
- Pluralize the readout ('1 conflict' not '1 conflicts'). Tests updated. Ui 128 green.

src/ClaudeDo.Ui/Views/Conflicts/ConflictResolverView.axaml.cs

@@ -40,6 +40,7 @@ public partial class ConflictResolverView : Window
     private bool _applyingAccept;
     private bool _syncing;
     private bool _gutterPending;
+    private int _gutterRetries;
 
     public ConflictResolverView()
     {
@@ -109,6 +110,7 @@ public partial class ConflictResolverView : Window
     {
         if (_vm is null) return;
         _rebuilding = true;
+        _gutterRetries = 0; // fresh retry budget for this file's gutter layout
         try
         {
             ClearGutters();
@@ -257,9 +259,12 @@ public partial class ConflictResolverView : Window
         var tv = ResultEditor.TextArea.TextView;
         if (!tv.VisualLinesValid)
         {
-            QueueGutters();
+            // Retry until the editor is laid out, but bounded so a never-laid-out editor
+            // (e.g. minimized window) can't busy-loop the dispatcher.
+            if (_gutterRetries++ < 40) QueueGutters();
             return;
         }
+        _gutterRetries = 0;
 
         var doc = ResultEditor.Document;
         foreach (var region in _resultRegions)