## Summary
- project effective marketplace/plugin config through the enterprise
source policy so blocked installed plugins become inactive
- filter plugin list/read/discovery and CLI marketplace source/snapshot
reporting using the same policy
- enforce source admission for background marketplace cache refreshes
- continue refreshing/upgrading independent marketplaces and plugins
when one entry fails, returning per-entry errors
- include policy-projected plugin state in cache and refresh keys so
requirement changes invalidate stale results
## Stack
This is PR 2 of 2 and is based on #29690. Review the admission model and
source matcher in #29690 first; this PR contains only runtime
enforcement.
## Test plan
- `just test -p codex-core-plugins` (287 tests)
- `just test -p codex-cli
plugin_list_ignores_implicit_system_marketplace_roots_without_manifests`
- `cargo check -p codex-cli -p codex-app-server --tests`