feat: add Grok 4.5 model

[Winds-AI]

Summary

• add the new Cursor Grok 4.5 model to the bundled fallback model snapshot
• retain the snapshot's existing context and output-token defaults

Verification

• npm test
• npm run typecheck

[het-e2m]

@offbynan I would like to see this merged.

[Winds-AI]

It might need a second look because i used sol to one shot this, it works properly in my pc so i've kept it as draft right now