Add script for removing OpenSpec artifacts

[carmandale]

Summary

• add a script to strip OpenSpec instructions or fully remove OpenSpec assets from a project
• support instructions-only mode for AGENTS.md/CLAUDE.md surgical cleanup
• document the new flag in the script header

[TabishB]

@carmandale Hey I understand the intention, but I'm not sure if this is the way to really implement this.

If the goal is it to uninstall or remove openspec config from a certain project we should extend the current cli to add this is an option with a confirmation flag/prompt.

It also dosen't make sense to add in a python dependency to the project for many reasons:

1. We can't expect users to have python installed
2. We don't have a way for supporting python dependencies
3. We dont have any testing config setup for python

[TabishB]

If you can update this to just be a cli command for openspec in standard typescript alongside proper unit tests, I'm happy to accept in the change.

[ericjuden]

Is this similar to the idea of the uninstall command?