several small model install enhancements

- Support extended HF repoid syntax in TUI. This allows
  installation of subfolders and safetensors files, as in
  `XpucT/Deliberate::Deliberate_v5.safetensors`

- Add `error` and `error_traceback` properties to the install
  job objects.

- Rename the `heuristic_import` route to `heuristic_install`.

- Fix the example `config` input in the `heuristic_install` route.

tests/app/services/model_install/test_model_install.py

@@ -256,4 +256,4 @@ def test_404_download(mm2_installer: ModelInstallServiceBase, mm2_app_config: In
     assert job.error_type == "HTTPError"
     assert job.error
     assert "NOT FOUND" in job.error
-    assert "Traceback" in job.error
+    assert job.error_traceback.startswith("Traceback")