feat(git): add ListLocalBranchesAsync

tests/ClaudeDo.Worker.Tests/Runner/GitServiceMergeTests.cs

@@ -34,4 +34,19 @@ public class GitServiceMergeTests : IDisposable
         Assert.True(branch == "main" || branch == "master",
             $"Expected main or master, got '{branch}'");
     }
+
+    [Fact]
+    public async Task ListLocalBranchesAsync_AfterCreatingSecondBranch_ReturnsBoth()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "feature/x");
+
+        var git = new GitService();
+        var branches = await git.ListLocalBranchesAsync(repo.RepoDir);
+
+        Assert.Contains("feature/x", branches);
+        Assert.True(branches.Any(b => b == "main" || b == "master"));
+    }
 }