Fix direct registry latest version selection

[abhinavgautam01]

Summary

Fixes #52.

This updates the direct registry fallback path for packages where LatestVersion is not populated by the registry response.

Changes

• Exclude unavailable versions when computing fallback latest version:
  • yanked
  • deprecated
  • retracted
• Use vers.CompareWithScheme with the PURL type instead of generic vers.Compare
• Add tests for unavailable status filtering
• Add coverage for scheme-specific ordering, including Debian-style versions

Testing

go test -run TestFindLatestVersion -v
go test ./...
git diff --check

[Copilot]

Pull request overview

Updates the direct-registry fallback logic used by RegistriesClient.BulkLookup when a registry response omits LatestVersion, ensuring “latest” selection respects both release availability and ecosystem-specific version ordering.

Changes:

• Filters out unavailable versions (yanked, deprecated, retracted) when computing the fallback latest version.
• Switches version comparison to vers.CompareWithScheme using the PURL type (ecosystem scheme).
• Expands unit tests to cover unavailable-status filtering and scheme-specific ordering (including Debian-style versions).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
registries.go	Computes fallback latest version using scheme-aware comparison and filters unavailable versions.
enrichment_test.go	Adds table-driven tests for unavailable statuses and scheme-specific ordering behavior.

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