Replace git branch with git worktree

[dpeckham]

Awesome work on Agent OS so far!!! Recently switched from spec-kit and loving Agent OS so far...

If Agent OS used git worktrees instead of branches, it would be more conducive to working on multiple specs at the same time. An alternative with be to have it skip git altogether and let the user manage it.

Thanks @CasJam!!!

[phpmacher]

Skip git was my idea also ;-) #160