fix: show guide for GitHub Copilot in github install command

[doozie-akshay]

Summary

• Removed the TODO comment in github.ts and added a helpful note when user cancels or doesn't select a provider
• When user cancels the provider selection or selects an invalid provider, they now see a message about GitHub Copilot availability with a link to setup docs

Added a helpful note that appears when:

1. User cancels the provider selection (presses Ctrl+C)
2. User doesn't select a valid provider from the list

The message informs users about GitHub Copilot availability and provides a link to setup documentation.

Related Issue

Closes Kilo-Org/kilocode#6311

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[doozie-akshay]

I've created an issue for this PR: Kilo-Org/kilocode#6311

[markijbema]

Hi! Thank you for taking the time to contribute to this project—we really appreciate it. 🙏

We are currently working on re-platforming the core of our VS Code and JetBrains extensions to be based on our new Kilo CLI, with a complete rebuild based on OpenCode as our new foundation, and the moment has come to promote this repository to become the main repository. To do that, we moved the code from this repository to the kilocode repository.

This unfortunately means we cannot merge this branch here anymore. Please add https://github.com/Kilo-Org/kilocode.git as a remote, and push your branch there and create a new PR in https://github.com/Kilo-Org/kilocode . We unfortunately cannot do this for you as then the PR would not be in your name anymore. If you need any help, feel free to ask on our Discord in #kilo-dev-contributors

Sorry for the inconvenience and thank you for contributing to Kilo!