## What changed
- Add a stable `sleep_tool` feature that can enable or disable registration of the built-in sleep tool independently of the clock tool.
- Support structured `features.sleep_tool` configuration with `model_driven` and `always_on` modes. The default `model_driven` mode preserves the existing model and `current_time_reminder` behavior, while `always_on` registers sleep whenever the feature is enabled.
- Preserve nested sleep-tool configuration across CLI overrides, config merges, and feature toggles, and expose the settings in the generated config schema.
## Testing
- Cover feature-map overrides, both selection modes, legacy clock settings, config merging and editing, and invalid mode rejection.
GitOrigin-RevId: 18eadc582f8a4445958c29d063e5be495276703e