fix(html): scope selector lists correctly

Co-Authored-By: Virgil <virgil@lethean.io>

responsive.go

@@ -81,7 +81,7 @@ func ScopeVariant(name, selector string) string {
 		return scope
 	}
 
-	parts := strings.Split(selector, ",")
+	parts := splitSelectorList(selector)
 	scoped := make([]string, 0, len(parts))
 	for i := range parts {
 		part := strings.TrimSpace(parts[i])
@@ -96,6 +96,69 @@ func ScopeVariant(name, selector string) string {
 	return strings.Join(scoped, ", ")
 }
 
+// splitSelectorList splits a CSS selector list on top-level commas only.
+// Commas inside brackets, parentheses, braces, or quoted strings are preserved.
+func splitSelectorList(selector string) []string {
+	if selector == "" {
+		return nil
+	}
+
+	parts := make([]string, 0, 1)
+	var b strings.Builder
+	var quote rune
+	depthParen := 0
+	depthBracket := 0
+	depthBrace := 0
+
+	for _, r := range selector {
+		switch {
+		case quote != 0:
+			b.WriteRune(r)
+			if r == quote {
+				quote = 0
+			} else if r == '\\' {
+				// Keep escaped characters inside quoted strings intact.
+				continue
+			}
+		case r == '"' || r == '\'':
+			quote = r
+			b.WriteRune(r)
+		case r == '(':
+			depthParen++
+			b.WriteRune(r)
+		case r == ')':
+			if depthParen > 0 {
+				depthParen--
+			}
+			b.WriteRune(r)
+		case r == '[':
+			depthBracket++
+			b.WriteRune(r)
+		case r == ']':
+			if depthBracket > 0 {
+				depthBracket--
+			}
+			b.WriteRune(r)
+		case r == '{':
+			depthBrace++
+			b.WriteRune(r)
+		case r == '}':
+			if depthBrace > 0 {
+				depthBrace--
+			}
+			b.WriteRune(r)
+		case r == ',' && depthParen == 0 && depthBracket == 0 && depthBrace == 0:
+			parts = append(parts, b.String())
+			b.Reset()
+		default:
+			b.WriteRune(r)
+		}
+	}
+
+	parts = append(parts, b.String())
+	return parts
+}
+
 // responsive.go: Variant adds a named layout variant (e.g., "desktop", "tablet", "mobile").
 // Example: r.Variant("mobile", NewLayout("C").C(Raw("body"))).
 // Variants render in insertion order.

responsive_test.go

@@ -215,3 +215,11 @@ func TestScopeVariant_IgnoresEmptySelectorSegments(t *testing.T) {
 		t.Fatalf("ScopeVariant should skip empty selector segments = %q, want %q", got, want)
 	}
 }
+
+func TestScopeVariant_PreservesNestedCommas(t *testing.T) {
+	got := ScopeVariant("desktop", `:is(.nav, .sidebar), .footer`)
+	want := `[data-variant="desktop"] :is(.nav, .sidebar), [data-variant="desktop"] .footer`
+	if got != want {
+		t.Fatalf("ScopeVariant should preserve nested commas = %q, want %q", got, want)
+	}
+}