fix(import[provenance]) Guard against non-dict metadata in provenance stamping

why: If a config entry has metadata as a non-dict value (e.g. a string),
setdefault("metadata", {}) returns the existing non-dict value and the
subsequent dict key assignment raises TypeError.
what:
- Add isinstance guard before setdefault at both UPDATE_URL and
  SKIP_UNCHANGED provenance-stamping call sites
- Add test_import_provenance_survives_non_dict_metadata verifying
  non-dict metadata is replaced with a proper dict

Author: tony

src/vcspull/cli/import_cmd/_common.py

@@ -952,6 +952,8 @@ def _run_import(
                 updated["repo"] = incoming_url
                 updated.pop("url", None)
                 if import_source:
+                    if not isinstance(updated.get("metadata"), (dict, type(None))):
+                        updated["metadata"] = {}
                     metadata = updated.setdefault("metadata", {})
                     metadata["imported_from"] = import_source
                 raw_config[repo_workspace_label][repo.name] = updated
@@ -963,6 +965,8 @@ def _run_import(
             if not dry_run and import_source:
                 live = raw_config[repo_workspace_label].get(repo.name)
                 if isinstance(live, dict):
+                    if not isinstance(live.get("metadata"), (dict, type(None))):
+                        live["metadata"] = {}
                     live.setdefault("metadata", {})["imported_from"] = import_source
                     provenance_tagged_count += 1
                 elif isinstance(live, str):

tests/cli/test_import_repos.py

@@ -3547,6 +3547,56 @@ def test_import_provenance_tagging_logs_message(
     assert "Tagged 1 repositories with import provenance" in caplog.text
 
 
+def test_import_provenance_survives_non_dict_metadata(
+    tmp_path: pathlib.Path,
+    monkeypatch: MonkeyPatch,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Provenance stamping replaces non-dict metadata with a proper dict."""
+    caplog.set_level(logging.INFO)
+    monkeypatch.setenv("HOME", str(tmp_path))
+    workspace = tmp_path / "repos"
+    workspace.mkdir()
+    config_file = tmp_path / ".vcspull.yaml"
+
+    # Existing entry with non-dict metadata — would crash without guard
+    save_config_yaml(
+        config_file,
+        {"~/repos/": {"repo1": {"repo": _SSH, "metadata": "legacy-string"}}},
+    )
+
+    importer = MockImporter(repos=[_make_repo("repo1")])
+    _run_import(
+        importer,
+        service_name="github",
+        target="testuser",
+        workspace=str(workspace),
+        mode="user",
+        language=None,
+        topics=None,
+        min_stars=0,
+        include_archived=False,
+        include_forks=False,
+        limit=100,
+        config_path_str=str(config_file),
+        dry_run=False,
+        yes=True,
+        output_json=False,
+        output_ndjson=False,
+        color="never",
+        sync=True,
+        import_source="github:testuser",
+    )
+
+    from vcspull._internal.config_reader import ConfigReader
+
+    final_config = ConfigReader._from_file(config_file)
+    assert final_config is not None
+    entry = final_config["~/repos/"]["repo1"]
+    assert isinstance(entry["metadata"], dict)
+    assert entry["metadata"]["imported_from"] == "github:testuser"
+
+
 # ---------------------------------------------------------------------------
 # --prune standalone flag tests
 # ---------------------------------------------------------------------------