Add native XBPS package support with runit service lifecycle: - packaging/xbps/install.sh: migration guard, fresh install (dormant), upgrade (snapshot, migrate, config preservation) - packaging/xbps/remove.sh: sanctioned disable, purge (full cleanup) - Makefile: package-xbps target with dependencies and config files - tests/test_packaging.py: 5 XBPS-specific tests + updated shared tests Acceptance criteria addressed: - Fresh install remains dormant; runit down marker set - Upgrade snapshots and migrates observation history safely - Removal performs sanctioned pause and retains history - Migration guard blocks install over make-install remnants - Debian/RPM regressions verified via existing shared tests Co-authored-by: CommandCodeBot <noreply@commandcode.ai>