Add support for Cursor's Agent CLI

[prathamdby]

The product is available at https://cursor.com/cli. It's genuinely a great CLI, and many a model performs better in it than in their own native harness.

Cursor provides first-class ACP support (if needed) with documentation available at https://cursor.com/docs/cli/acp. Any other reference can be found at https://cursor.com/docs/cli/overview.