fix(trainer): validate HuggingFace storage_uri has both user and repo

[SahilKumar75]

What this does

Follow-up to #564. The HuggingFace initializers only rejected a storage_uri with an empty path, so URIs missing either component were still accepted and only failed later at download time:

• hf://user/ (no repo name)
• hf:///model (no user name)

HuggingFaceDatasetInitializer also had no test coverage for its validation.

The fix

Consolidate the validation into a shared _validate_hf_storage_uri helper used by both HuggingFaceModelInitializer and HuggingFaceDatasetInitializer, requiring a non-empty user and repo. Valid URIs such as hf://user/model are unchanged.

Testing

• Added a parametrized test for HuggingFaceDatasetInitializer (previously uncovered) and new rejected-form cases for both initializers.
• make test-python: 404 passed.
• make verify: all checks passed.

[Copilot]

Pull request overview

This PR tightens early validation of HuggingFace storage_uri values used by Trainer initializers so malformed hf:// URIs (missing either the user or repo component) fail fast at construction time instead of later during download.

Changes:

• Added a shared _validate_hf_storage_uri(storage_uri, entity) helper and used it from both HuggingFaceModelInitializer and HuggingFaceDatasetInitializer.
• Expanded unit tests to cover HuggingFaceDatasetInitializer validation and added additional invalid storage_uri cases (missing user or repo).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
kubeflow/trainer/types/types.py	Consolidates HuggingFace storage_uri validation and enforces both user and repo components for model/dataset initializers.
kubeflow/trainer/types/types_test.py	Adds parametrized tests for both HuggingFace initializers, including newly rejected URI forms.

[andreyvelich]

/ok-to-test
/retest
/lgtm
/approve

Thanks @SahilKumar75!
/cc @akshaychitneni

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andreyvelich

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [andreyvelich]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment