Attribute executor skill invocations to plugins (#39309)

## What changed

- Carry selected plugin identities from MCP discovery into per-turn extension data, limited to capability roots that are ready for the turn.
- Annotate executor skill catalog entries with the matching plugin ID and `user` scope.
- Include that attribution in `skill_invocation` analytics for both explicit and implicit executor skill invocations.

## Testing

- Extend the executor skills app-server test to verify plugin ID, skill scope, and invocation type for explicit and implicit analytics events.

GitOrigin-RevId: 9345600ae29bcb8eb894fffd2d6f7b05f22ebf74

codex-rs/ext/skills/src/provider.rs

@@ -22,6 +22,7 @@ use crate::catalog::SkillResourceId;
 use crate::catalog::SkillSearchResult;
 
 pub use executor::ExecutorSkillProvider;
+pub(crate) use executor::attribute_executor_plugins;
 pub use host::HostSkillProvider;
 pub use orchestrator::OrchestratorSkillProvider;