feat(git): add ListConflictedFilesAsync

src/ClaudeDo.Data/Git/GitService.cs

@@ -198,6 +198,19 @@ public sealed class GitService
             throw new InvalidOperationException($"git merge --abort failed (exit {exitCode}): {stderr}");
     }
 
+    public async Task<List<string>> ListConflictedFilesAsync(string repoDir, CancellationToken ct = default)
+    {
+        var (exitCode, stdout, stderr) = await RunGitAsync(repoDir,
+            ["diff", "--name-only", "--diff-filter=U"], ct);
+        if (exitCode != 0)
+            throw new InvalidOperationException($"git diff --diff-filter=U failed (exit {exitCode}): {stderr}");
+
+        return stdout
+            .Split('\n', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
+            .Where(s => s.Length > 0)
+            .ToList();
+    }
+
     public async Task MergeFfOnlyAsync(string repoDir, string branchName, CancellationToken ct = default)
     {
         var (exitCode, _, stderr) = await RunGitAsync(repoDir, ["merge", "--ff-only", branchName], ct);