feat(pacman): implement Manager interface for pacman package manager

Adds full pacman wrapper with:
- All Manager interface methods (Install, Remove, Purge, Upgrade, Update,
  List, Search, Info, IsInstalled, Version, Available)
- Linux implementation using exec.CommandContext
- Non-linux stubs returning ErrUnsupportedPlatform
- Output parsing for -Q, -Ss, -Si formats
- Options support: WithSudo, WithAssumeYes, WithDryRun, WithRoot
- Unit tests for parsing and argument building

pacman/pacman_other.go

@@ -0,0 +1,51 @@
+//go:build !linux
+
+package pacman
+
+import (
+	"context"
+
+	"github.com/gogrlx/snack"
+)
+
+func available() bool { return false }
+
+func install(_ context.Context, _ []string, _ ...snack.Option) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func remove(_ context.Context, _ []string, _ ...snack.Option) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func purge(_ context.Context, _ []string, _ ...snack.Option) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func upgrade(_ context.Context, _ ...snack.Option) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func update(_ context.Context) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func list(_ context.Context) ([]snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func search(_ context.Context, _ string) ([]snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func info(_ context.Context, _ string) (*snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func isInstalled(_ context.Context, _ string) (bool, error) {
+	return false, snack.ErrUnsupportedPlatform
+}
+
+func version(_ context.Context, _ string) (string, error) {
+	return "", snack.ErrUnsupportedPlatform
+}