fix(classifypkg): tag Rust static musl builds as libc='none'

Rust *-unknown-linux-musl builds are statically linked with zero
runtime libc dependency. Detect this pattern in classifyGitHub and
override libc from 'musl' to 'none'. Hard-musl packages (pwsh, bun,
node) use different filename patterns and keep libc='musl'.

internal/classifypkg/classifypkg.go

@@ -14,6 +14,9 @@ import (
 	"strings"
 	"time"
 
+	"regexp"
+
+	"github.com/webinstall/webi-installers/internal/buildmeta"
 	"github.com/webinstall/webi-installers/internal/classify"
 	"github.com/webinstall/webi-installers/internal/installerconf"
 	"github.com/webinstall/webi-installers/internal/rawcache"
@@ -305,6 +308,13 @@ type ghAsset struct {
 	Size               int64  `json:"size"`
 }
 
+// reRustMuslStatic matches Rust target triples that indicate a statically-linked
+// musl build. Rust's *-unknown-linux-musl targets are always static — they have
+// zero runtime libc dependency. This is distinct from packages like pwsh
+// (-linux-musl-x64), bun (-linux-x64-musl), and node (-linux-x64-musl) which
+// dynamically link against musl and require it at runtime.
+var reRustMuslStatic = regexp.MustCompile(`(?i)-unknown-linux-musl`)
+
 func classifyGitHub(pkg string, conf *installerconf.Conf, d *rawcache.Dir) ([]storage.Asset, error) {
 	tagPrefix := conf.TagPrefix
 	releases, err := ReadAllRaw(d)
@@ -356,13 +366,19 @@ func classifyGitHub(pkg string, conf *installerconf.Conf, d *rawcache.Dir) ([]st
 				name = name[:len(name)-4] + ".tar.gz"
 			}
 
+			libc := r.Libc
+			// Rust static musl builds have zero runtime libc dependency.
+			if libc == buildmeta.LibcMusl && reRustMuslStatic.MatchString(a.Name) {
+				libc = buildmeta.LibcNone
+			}
+
 			assets = append(assets, storage.Asset{
 				Filename: name,
 				Version:  version,
 				Channel:  channel,
 				OS:       string(r.OS),
 				Arch:     string(r.Arch),
-				Libc:     string(r.Libc),
+				Libc:     string(libc),
 				Format:   string(r.Format),
 				Download: a.BrowserDownloadURL,
 				Date:     date,

internal/resolve/resolve_cache_test.go

@@ -320,26 +320,29 @@ func TestResolvePosixPackages(t *testing.T) {
 	}
 }
 
-// TestResolveLibcPreference tests musl vs gnu selection.
+// TestResolveLibcPreference tests libc selection.
+// bat is a Rust project — its musl builds are static (libc='none').
+// pwsh has hard musl dependencies (libc='musl').
 func TestResolveLibcPreference(t *testing.T) {
-	dists := loadCacheDists(t, "bat")
+	batDists := loadCacheDists(t, "bat")
 
-	// Explicit musl request.
-	m := resolve.Best(dists, resolve.Query{
+	// Musl host requesting bat: gets the static musl build (tagged 'none').
+	m := resolve.Best(batDists, resolve.Query{
 		OS:      buildmeta.OSLinux,
 		Arch:    buildmeta.ArchAMD64,
 		Libc:    buildmeta.LibcMusl,
 		Formats: []string{".tar.gz"},
 	})
 	if m == nil {
-		t.Fatal("expected musl match")
+		t.Fatal("expected match for musl host")
 	}
-	if m.Libc != "musl" {
-		t.Errorf("Libc = %q, want musl", m.Libc)
+	// Rust musl builds are static — tagged as 'none', not 'musl'.
+	if m.Libc != "none" {
+		t.Errorf("bat musl request: Libc = %q, want none (static musl)", m.Libc)
 	}
 
 	// Explicit gnu request.
-	m = resolve.Best(dists, resolve.Query{
+	m = resolve.Best(batDists, resolve.Query{
 		OS:      buildmeta.OSLinux,
 		Arch:    buildmeta.ArchAMD64,
 		Libc:    buildmeta.LibcGNU,
@@ -352,8 +355,8 @@ func TestResolveLibcPreference(t *testing.T) {
 		t.Errorf("Libc = %q, want gnu", m.Libc)
 	}
 
-	// No preference — should still match (accepts either).
-	m = resolve.Best(dists, resolve.Query{
+	// No preference — should still match (accepts any).
+	m = resolve.Best(batDists, resolve.Query{
 		OS:      buildmeta.OSLinux,
 		Arch:    buildmeta.ArchAMD64,
 		Formats: []string{".tar.gz"},
@@ -361,6 +364,21 @@ func TestResolveLibcPreference(t *testing.T) {
 	if m == nil {
 		t.Fatal("expected match with no libc preference")
 	}
+
+	// pwsh has hard musl builds (dynamically linked, requires musl runtime).
+	pwshDists := loadCacheDists(t, "pwsh")
+	m = resolve.Best(pwshDists, resolve.Query{
+		OS:      buildmeta.OSLinux,
+		Arch:    buildmeta.ArchAMD64,
+		Libc:    buildmeta.LibcMusl,
+		Formats: []string{".tar.gz"},
+	})
+	if m == nil {
+		t.Fatal("expected pwsh musl match")
+	}
+	if m.Libc != "musl" {
+		t.Errorf("pwsh musl request: Libc = %q, want musl", m.Libc)
+	}
 }
 
 // TestResolveFormatFallback tests format preference cascading.

internal/resolver/resolver_cache_test.go

@@ -250,20 +250,21 @@ func TestCacheGitPackages(t *testing.T) {
 }
 
 // TestCacheLibcPreference tests explicit libc selection.
+// bat is Rust — its musl builds are static (tagged 'none').
 func TestCacheLibcPreference(t *testing.T) {
 	assets := loadAssets(t, "bat")
 
-	// Explicit musl.
+	// Musl host requesting bat: gets static musl build (tagged 'none').
 	res, err := resolver.Resolve(assets, resolver.Request{
 		OS:   "linux",
 		Arch: "x86_64",
 		Libc: "musl",
 	})
 	if err != nil {
-		t.Fatal("expected musl match")
+		t.Fatal("expected match for musl host")
 	}
-	if res.Asset.Libc != "musl" {
-		t.Errorf("Libc = %q, want musl", res.Asset.Libc)
+	if res.Asset.Libc != "none" {
+		t.Errorf("Libc = %q, want none (static musl)", res.Asset.Libc)
 	}
 
 	// Explicit gnu.