feat(ui): show mergeability and surface approve conflicts in the work console

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

src/ClaudeDo.Ui/ViewModels/Islands/MergePreviewPresenter.cs

@@ -0,0 +1,28 @@
+using System.Linq;
+using ClaudeDo.Ui.Services;
+
+namespace ClaudeDo.Ui.ViewModels.Islands;
+
+/// Pure mapping from a merge-preview DTO to display text + color flags.
+public static class MergePreviewPresenter
+{
+    public static (string Text, bool IsClean, bool IsConflict) Describe(MergePreviewDto? dto)
+    {
+        if (dto is null) return ("", false, false);
+
+        switch (dto.Status)
+        {
+            case "clean":
+                var unit = dto.ChangedFileCount == 1 ? "file" : "files";
+                return ($"Merges cleanly · {dto.ChangedFileCount} {unit}", true, false);
+
+            case "conflict":
+                var names = string.Join(", ", dto.ConflictFiles.Take(3));
+                var more = dto.ConflictFiles.Count > 3 ? $" (+{dto.ConflictFiles.Count - 3} more)" : "";
+                return ($"Conflicts in {names}{more}", false, true);
+
+            default:
+                return ("Mergeability unknown", false, false);
+        }
+    }
+}