feat: initial project scaffold

- 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

types.go

@@ -0,0 +1,57 @@
+package snack
+
+// Package represents a system package.
+type Package struct {
+	Name        string `json:"name"`
+	Version     string `json:"version"`
+	Description string `json:"description,omitempty"`
+	Arch        string `json:"arch,omitempty"`
+	Repository  string `json:"repository,omitempty"`
+	Installed   bool   `json:"installed"`
+}
+
+// Options holds configuration for package manager operations.
+type Options struct {
+	Sudo      bool
+	AssumeYes bool
+	DryRun    bool
+	Root      string // alternate root filesystem
+	Verbose   bool
+}
+
+// Option is a functional option for package manager operations.
+type Option func(*Options)
+
+// WithSudo runs the command with sudo.
+func WithSudo() Option {
+	return func(o *Options) { o.Sudo = true }
+}
+
+// WithAssumeYes automatically confirms prompts.
+func WithAssumeYes() Option {
+	return func(o *Options) { o.AssumeYes = true }
+}
+
+// WithDryRun simulates the operation without making changes.
+func WithDryRun() Option {
+	return func(o *Options) { o.DryRun = true }
+}
+
+// WithRoot sets an alternate root filesystem path.
+func WithRoot(root string) Option {
+	return func(o *Options) { o.Root = root }
+}
+
+// WithVerbose enables verbose output.
+func WithVerbose() Option {
+	return func(o *Options) { o.Verbose = true }
+}
+
+// ApplyOptions processes functional options into an Options struct.
+func ApplyOptions(opts ...Option) Options {
+	var o Options
+	for _, opt := range opts {
+		opt(&o)
+	}
+	return o
+}