feature: uninstall command

[rekram1-node]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

It'd be useful to have an uninstall command that cleans up all the opencode related files.

Read global/index.ts to see where some of these are. Also consider reading installation/index.ts, if uninstalling for a package manager you prolly want to go through their process of uninstalling rather than just deleting the file executing current process.

AC: opencode uninstall command

[github-actions[bot]]

This issue might be a duplicate of existing issues. Please check:

• #14: Both request an uninstall command/script that cleans up all application files and configurations

Feel free to ignore if none of these address your specific case.