chore: remove ruflo and frontend-design — full cleanup
Both plugins removed from all config, scripts, and documentation:
- ruflo: uninstalled globally (npm), removed from install/update/doctor/session-start/detect/lock/advisor
- frontend-design: removed from install/session-start/detect/advisor (was already commented out)
- plugin-advisor.md: compatibility matrix, decision table, conditional rules, recommended sets all updated
- README.md/USAGE.md: all references cleaned, token cost estimates recalculated
- install-plugins.sh: steps renumbered (10→9 steps)
- CHANGELOG.md: kept as historical record
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>