feat(layout): render empty variant slots

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

layout.go

@@ -80,9 +80,6 @@ func (l *Layout) Render(ctx *Context) string {
 	for i := range len(l.variant) {
 		slot := l.variant[i]
 		children := l.slots[slot]
-		if len(children) == 0 {
-			continue
-		}
 
 		meta, ok := slotRegistry[slot]
 		if !ok {

layout_test.go

@@ -114,3 +114,16 @@ func TestLayout_IgnoresInvalidSlots(t *testing.T) {
 		t.Errorf("C variant should ignore R slot content, got:\n%s", got)
 	}
 }
+
+func TestLayout_RendersEmptySlots(t *testing.T) {
+	ctx := NewContext()
+	layout := NewLayout("HCF")
+
+	got := layout.Render(ctx)
+
+	for _, want := range []string{`<header role="banner" data-block="H-0"></header>`, `<main role="main" data-block="C-0"></main>`, `<footer role="contentinfo" data-block="F-0"></footer>`} {
+		if !strings.Contains(got, want) {
+			t.Errorf("empty slot should still render %q in:\n%s", want, got)
+		}
+	}
+}