## Why
The model provider does not reliably identify which curated plugin catalog is
available. ChatGPT authentication can be used with a custom provider, while an
unauthenticated session should use the API-compatible catalog regardless of its
provider.
## What changed
- Select the ChatGPT curated catalog only for authentication modes that use the
Codex backend; use the API curated catalog for API-key and unauthenticated
sessions.
- Initialize standalone plugin managers with the current authentication mode
across CLI, app-server, MCP, and external-agent migration paths.
- Preserve authentication mode while detecting and importing migrated plugins.
## Testing
- Cover catalog and skill routing across ChatGPT, API-key, unauthenticated,
Bedrock, and custom-provider configurations.
- Verify authenticated plugin migration uses the ChatGPT curated marketplace.
GitOrigin-RevId: 660a339ee8891c33aad961078d3a979242a6a166