fix: use working clones for git repos

- Create normal working clones for remote repositories
- Initialize blank repositories with a main branch
- Align pull and branch helpers with unborn HEAD handling
- Gate fetch/pull on repositories with a remote

Quality gates: vitest repositories-settings-tab (passed); api pytest blocked by missing fastapi in environment

apps/api/tests/integration/test_git_control.py

@@ -63,6 +63,13 @@ class TestGitStatus:
         assert "new.py" in status.untracked
 
 
+def test_get_current_branch_handles_unborn_main() -> None:
+    with tempfile.TemporaryDirectory() as tmpdir:
+        os.system(f"git init -b main {tmpdir} >/dev/null 2>&1")
+
+        assert get_current_branch(tmpdir) == "main"
+
+
 class TestBranchOperations:
     """Tests for branch management functions."""