feat: implement detect package and snack CLI

- detect: auto-detection with Default(), All(), ByName()
  - Platform-specific probing via build tags (linux, freebsd, openbsd)
  - Linux probe order: apt, dnf, pacman, apk, flatpak, snap
- cmd/snack: full CLI with cobra + charmbracelet/fang
  - Subcommands: install, remove, purge, upgrade, update, list, search,
    info, which, hold, unhold, clean, detect, version
  - Global flags: --manager, --sudo, --yes, --dry-run
  - Capability type-assertions for FileOwner, Holder, Cleaner
- detect: basic compilation tests

pkg/parse.go

@@ -0,0 +1,162 @@
+package pkg
+
+import (
+	"strings"
+
+	"github.com/gogrlx/snack"
+)
+
+// parseQuery parses the output of `pkg query '%n\t%v\t%c'`.
+func parseQuery(output string) []snack.Package {
+	var pkgs []snack.Package
+	for _, line := range strings.Split(output, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		parts := strings.SplitN(line, "\t", 3)
+		if len(parts) < 2 {
+			continue
+		}
+		p := snack.Package{
+			Name:      parts[0],
+			Version:   parts[1],
+			Installed: true,
+		}
+		if len(parts) == 3 {
+			p.Description = parts[2]
+		}
+		pkgs = append(pkgs, p)
+	}
+	return pkgs
+}
+
+// parseSearch parses the output of `pkg search <query>`.
+// Format: "name-version                Comment text"
+func parseSearch(output string) []snack.Package {
+	var pkgs []snack.Package
+	for _, line := range strings.Split(output, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		// Split on whitespace; first field is name-version
+		parts := strings.SplitN(line, " ", 2)
+		nameVer := parts[0]
+		name, ver := splitNameVersion(nameVer)
+		p := snack.Package{
+			Name:    name,
+			Version: ver,
+		}
+		if len(parts) == 2 {
+			p.Description = strings.TrimSpace(parts[1])
+		}
+		pkgs = append(pkgs, p)
+	}
+	return pkgs
+}
+
+// parseInfo parses the output of `pkg info <pkg>`.
+// Format is "Key: Value" lines.
+func parseInfo(output string) *snack.Package {
+	pkg := &snack.Package{Installed: true}
+	for _, line := range strings.Split(output, "\n") {
+		idx := strings.Index(line, ":")
+		if idx < 0 {
+			continue
+		}
+		key := strings.TrimSpace(line[:idx])
+		val := strings.TrimSpace(line[idx+1:])
+		switch key {
+		case "Name":
+			pkg.Name = val
+		case "Version":
+			pkg.Version = val
+		case "Comment":
+			pkg.Description = val
+		case "Arch":
+			pkg.Arch = val
+		}
+	}
+	if pkg.Name == "" {
+		return nil
+	}
+	return pkg
+}
+
+// parseUpgrades parses the output of `pkg upgrade -n`.
+// Looks for lines like:
+//
+//	Installing pkg-name: oldver -> newver
+//	Upgrading pkg-name: oldver -> newver
+func parseUpgrades(output string) []snack.Package {
+	var pkgs []snack.Package
+	for _, line := range strings.Split(output, "\n") {
+		line = strings.TrimSpace(line)
+		// Look for "Upgrading" or "Reinstalling" lines with ->
+		if !strings.Contains(line, "->") {
+			continue
+		}
+		var nameVer string
+		if strings.HasPrefix(line, "Upgrading ") {
+			nameVer = strings.TrimPrefix(line, "Upgrading ")
+		} else if strings.HasPrefix(line, "Installing ") {
+			nameVer = strings.TrimPrefix(line, "Installing ")
+		} else if strings.HasPrefix(line, "Reinstalling ") {
+			nameVer = strings.TrimPrefix(line, "Reinstalling ")
+		} else {
+			continue
+		}
+		// "name: oldver -> newver"
+		colonIdx := strings.Index(nameVer, ":")
+		if colonIdx < 0 {
+			continue
+		}
+		name := strings.TrimSpace(nameVer[:colonIdx])
+		rest := strings.TrimSpace(nameVer[colonIdx+1:])
+		parts := strings.Fields(rest)
+		if len(parts) >= 3 && parts[1] == "->" {
+			pkgs = append(pkgs, snack.Package{
+				Name:      name,
+				Version:   parts[2],
+				Installed: true,
+			})
+		}
+	}
+	return pkgs
+}
+
+// parseFileList parses `pkg info -l <pkg>` output.
+// Lines starting with "/" after the header are file paths.
+func parseFileList(output string) []string {
+	var files []string
+	for _, line := range strings.Split(output, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "/") {
+			files = append(files, line)
+		}
+	}
+	return files
+}
+
+// parseOwner parses `pkg which <path>` output.
+// Format: "/path was installed by package name-version"
+func parseOwner(output string) string {
+	output = strings.TrimSpace(output)
+	if idx := strings.Index(output, "was installed by package "); idx != -1 {
+		remainder := output[idx+len("was installed by package "):]
+		name, _ := splitNameVersion(strings.TrimSpace(remainder))
+		return name
+	}
+	return output
+}
+
+// splitNameVersion splits "name-version" into name and version.
+// FreeBSD pkg uses the last hyphen as separator (name can contain hyphens).
+func splitNameVersion(s string) (string, string) {
+	idx := strings.LastIndex(s, "-")
+	if idx <= 0 {
+		return s, ""
+	}
+	return s[:idx], s[idx+1:]
+}