Add `bmad uninstall` CLI command for clean removal of BMAD installations.
Interactive mode with directory router and component multiselect; non-interactive
`--yes` flag preserves user artifacts by default. Three-phase spinner UX,
manifest-scoped IDE cleanup, GitHub Copilot marker stripping, recursive empty
directory cleanup, and chalk-to-clack migration in copilot handler.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Davor Racić
Brian Madison