## Summary
- Move plugin discoverable recommendation filtering from `codex-core`
into `codex-core-plugins` behind `ToolSuggestPluginDiscoveryInput`.
- Keep `codex-core` as a thin adapter from `Config` to the core-plugins
API and back to `DiscoverablePluginInfo`.
- Keep the existing discoverable allowlist private to the core-plugins
implementation.
## Validation
- `just fmt`
- `just test -p codex-core list_tool_suggest_discoverable_plugins`
- `git diff --check`
- Read-only subagent review: no findings