test: add unit tests for plugin_health_dashboard helpers

[kumbharkajal]

Summary

• Add unit tests for safe_relative_path
• Add unit tests for discover_plugins
• Cover empty plugin directories
• Cover missing plugin directories
• Cover invalid metadata.json
• Cover plugins with and without parser.py
• Verify plugin sorting
• Verify metadata fallback behavior

Closes #1643

[utksh1]

The helper coverage is reasonable, but this branch is behind main and fails backend-unit. Please rebase, fix the failing suite, and coordinate with the duplicate/stacked plugin-health test branches so this test file has one canonical PR.

[utksh1]

The helper coverage is reasonable, but this branch is behind main and fails backend-unit. Please rebase, fix the failing suite, and coordinate with the duplicate/stacked plugin-health test branches so this test file has one canonical PR.

[utksh1]

Please rebase and fix the failing backend-unit check. Keep the helper tests concise and fixture-driven; avoid duplicating the broader stacked test suite already under review in #2079.

[kumbharkajal]

Hi @utksh1,

I've rebased my branch onto the latest main and force-pushed the updated branch.

Regarding the duplicate helper tests, my PR is focused only on the safe_relative_path and discover_plugins helper coverage for issue #1643. I'll defer to your preference on keeping a single canonical PR for this test file if you'd like these changes consolidated with #2079.

The backend-unit check is still failing, but the failures appear to be in unrelated test modules (test_saved_views.py and test_parser_sandbox_timeout_cleanup.py), which aren't touched by this PR. Please let me know if you'd like me to investigate those failures further or if they're already being handled elsewhere.