## Why
Marketplace source restrictions should cover curated plugins backed by the OpenAI plugins repository, not only user-configured marketplaces.
## What changed
- Validate both local curated catalogs against the existing OpenAI plugins Git source allowlist.
- Apply that policy to catalog discovery, installation, cached plugin and skill loading, and startup repository sync.
- Keep bundled and remote installed plugins independent of the curated Git source policy.
## Testing
Added coverage for exact and shorthand Git allowlist entries, host patterns, blocked and invalid rules, curated catalog variants, plugin skills, startup sync, and remote installed plugins.
GitOrigin-RevId: 04617acb4a93040c70a13759eb4ce872877ba211