[Feature]: Support Copilot CLI

[sxsong1207]

Problem or motivation

Thank you for the great project! I have use it to build my bot and it works very well! Is it possible to support Github's Copilot CLI as well?

Proposed solution

Enable the bot bridge with Github Copilot CLI
https://github.com/features/copilot/cli

Alternatives considered

No response

Before submitting

• I have searched existing issues and feature requests for duplicates.

[PleasePrompto]

Status update: deferring to the next milestone. Adding Copilot would make it the 5th provider, and the more important work is to generalize the provider layer first (there's an ongoing thread on that alongside #102 and the earlier PR #100). I'll document the BaseCLI extension path in docs/architecture.md as a follow-up so future providers drop in cleanly. Leaving this open — will link to the tracking issue for the provider-extensibility phase when it's scoped.