feat: add Homebrew provider, implement NameNormalizer across all managers

- Add brew package for Homebrew support on macOS and Linux
- Implement NameNormalizer interface (NormalizeName, ParseArch) for all providers
- Add darwin platform detection with Homebrew as default
- Consolidate capabilities by removing separate *_linux.go/*_other.go files
- Update tests for new capability expectations
- Add comprehensive tests for AUR and brew providers
- Update README with capability matrix and modern Target API usage

💘 Generated with Crush

Assisted-by: AWS Claude Opus 4.5 via Crush <crush@charm.land>

pkg/capabilities.go

@@ -11,6 +11,7 @@ var (
 	_ snack.VersionQuerier = (*Pkg)(nil)
 	_ snack.Cleaner        = (*Pkg)(nil)
 	_ snack.FileOwner      = (*Pkg)(nil)
+	_ snack.NameNormalizer = (*Pkg)(nil)
 )
 
 // LatestVersion returns the latest available version from configured repositories.

pkg/normalize.go

@@ -0,0 +1,17 @@
+package pkg
+
+// normalizeName returns the canonical form of a package name.
+// FreeBSD pkg package names use "name-version" format. This function
+// strips the version portion if present, returning just the name.
+func normalizeName(name string) string {
+	n, _ := splitNameVersion(name)
+	return n
+}
+
+// parseArchNormalize extracts the architecture from a package name if present.
+// FreeBSD pkg package names do not embed architecture in the name itself
+// (the arch is separate metadata), so this returns the name unchanged with
+// an empty architecture string.
+func parseArchNormalize(name string) (string, string) {
+	return name, ""
+}

pkg/pkg.go

@@ -83,6 +83,16 @@ func (p *Pkg) Version(ctx context.Context, pkg string) (string, error) {
 	return version(ctx, pkg)
 }
 
+// NormalizeName returns the canonical form of a package name.
+func (p *Pkg) NormalizeName(name string) string {
+	return normalizeName(name)
+}
+
+// ParseArch extracts the architecture from a package name if present.
+func (p *Pkg) ParseArch(name string) (string, string) {
+	return parseArchNormalize(name)
+}
+
 // Verify interface compliance at compile time.
 var _ snack.Manager = (*Pkg)(nil)
 var _ snack.PackageUpgrader = (*Pkg)(nil)

pkg/pkg_test.go

@@ -659,8 +659,8 @@ func TestCapabilities(t *testing.T) {
 	if caps.Groups {
 		t.Error("expected Groups=false")
 	}
-	if caps.NameNormalize {
-		t.Error("expected NameNormalize=false")
+	if !caps.NameNormalize {
+		t.Error("expected NameNormalize=true")
 	}
 	if caps.DryRun {
 		t.Error("expected DryRun=false")