Add registry badge regression tests

[weich97]

Scope

Add tests that ensure the community registry keeps entry IDs, reproducibility badges, redaction badges, sorting metadata, and detail panels.

Suggested files

• tests/
• src/tradearena/evaluation/submissions.py

Acceptance criteria

• The HTML output includes Reproducible and Redacted badges for accepted rows.
• Entry IDs are stable for a given reproducibility hash.
• Empty registry output still renders.

Validation

python -m pytest tests/test_benchmark_submission.py -q