<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Copilot now defaults to the updated Claude Sonnet 4.5 model across
experiences for improved responses.
* **Chores**
* Consolidated available Anthropic models, removing older Sonnet 3.x
variants and standardizing Sonnet 4/4.5 options.
* Updated configuration defaults and schema mappings to reference the
new Sonnet 4.5 model.
* **Tests**
* Updated unit and end-to-end tests to reference the new model to ensure
consistent behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->