Elevate Attestation as a First-Class Object in Repository UI and Security Overview [Public Preview]

### Value Prop
You can now easily view and verify attestations directly in your repository’s UI and Security Overview, with clear SLSA level indicators. This makes it simpler for developers, security admins, and compliance leads to assess trust and compliance at a glance, streamlining your security workflows.

### Expected Outcome
By making attestations a first-class part of the repository experience, we aim to reduce friction and increase adoption of secure development practices. This change helps enterprise teams meet SLSA source track requirements and strengthens trust in your software supply chain.