- Add snack.Locker embed for per-provider mutex serialization
- Update all providers (pacman, apk, apt, dpkg) to use []Target
with version pinning support (pkg=version syntax)
- Add lock/unlock to all mutating operations (Install, Remove, Purge,
Upgrade, Update)
- Add snack.TargetNames helper and formatTargets per provider
- apt: add FromRepo (-t) and Reinstall support
- dpkg: use Target.Source for .deb file paths in Install
