Pass 1 (Feature & Completeness): - Replace apt CLI with apt-get for listUpgrades (apt CLI is unstable for scripting) - Verify snapd daemon is running in snap Available() check - Add ErrDaemonNotRunning sentinel error for daemon-dependent managers - Fix staticcheck S1011: replace loop with append(keys, matches...) - Fix staticcheck SA1012: use context.TODO() instead of nil in dpkg tests
- Common Manager interface, Package type, functional options - Sentinel errors for common package manager failures - Sub-package stubs for: pacman, aur, apk, apt, dpkg, dnf, rpm, flatpak, snap, pkg (FreeBSD), ports (OpenBSD) - detect/ package for auto-detection of system package manager - 0BSD license
