Gate reasoning effort updates on explicit model support - #46530

## Why

Using Responses Lite does not establish whether a model accepts reasoning-effort `configuration_update` items. Unsupported models need to use the selected request-level effort, including when resuming history containing saved updates.

## What changed

- Add `supports_reasoning_effort_updates` model metadata, defaulting to `false`.
- Require the override feature, an OpenAI provider, and explicit model support for reasoning effort updates, independently of `use_responses_lite`.
- Filter saved configuration updates from unsupported requests without changing persisted history.
- Clear the pinned effort baseline when sampling with an unsupported model so returning to a supported model establishes a fresh baseline. Compaction uses the selected effort without clearing the pin.

## Testing

Add coverage for supported models with either Responses mode, unsupported-model history filtering over HTTP and WebSocket, switching to an unsupported model and back, and compaction versus sampling pin behavior. Verify missing capability metadata defaults to `false`.

GitOrigin-RevId: 8a0fbc141964bd854dbcdd6f31e1c8e97697cf22