feat: add StripTags for render-reverse pipeline

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pipeline.go

@@ -0,0 +1,30 @@
+package html
+
+import "strings"
+
+// StripTags removes HTML tags from rendered output, returning plain text.
+// Tag boundaries are replaced with a single space; result is trimmed.
+func StripTags(html string) string {
+	var b strings.Builder
+	inTag := false
+	for _, r := range html {
+		if r == '<' {
+			inTag = true
+			b.WriteByte(' ')
+			continue
+		}
+		if r == '>' {
+			inTag = false
+			continue
+		}
+		if !inTag {
+			b.WriteRune(r)
+		}
+	}
+	// Collapse multiple spaces into one.
+	result := b.String()
+	for strings.Contains(result, "  ") {
+		result = strings.ReplaceAll(result, "  ", " ")
+	}
+	return strings.TrimSpace(result)
+}

pipeline_test.go

@@ -0,0 +1,49 @@
+package html
+
+import "testing"
+
+func TestStripTags_Simple(t *testing.T) {
+	got := StripTags(`<div>hello</div>`)
+	want := "hello"
+	if got != want {
+		t.Errorf("StripTags(<div>hello</div>) = %q, want %q", got, want)
+	}
+}
+
+func TestStripTags_Nested(t *testing.T) {
+	got := StripTags(`<header role="banner"><h1>Title</h1></header>`)
+	want := "Title"
+	if got != want {
+		t.Errorf("StripTags(nested) = %q, want %q", got, want)
+	}
+}
+
+func TestStripTags_MultipleRegions(t *testing.T) {
+	got := StripTags(`<header>Head</header><main>Body</main><footer>Foot</footer>`)
+	want := "Head Body Foot"
+	if got != want {
+		t.Errorf("StripTags(multi) = %q, want %q", got, want)
+	}
+}
+
+func TestStripTags_Empty(t *testing.T) {
+	got := StripTags("")
+	if got != "" {
+		t.Errorf("StripTags(\"\") = %q, want empty", got)
+	}
+}
+
+func TestStripTags_NoTags(t *testing.T) {
+	got := StripTags("plain text")
+	if got != "plain text" {
+		t.Errorf("StripTags(plain) = %q, want %q", got, "plain text")
+	}
+}
+
+func TestStripTags_Entities(t *testing.T) {
+	got := StripTags(`&lt;script&gt;`)
+	want := "&lt;script&gt;"
+	if got != want {
+		t.Errorf("StripTags should preserve entities, got %q, want %q", got, want)
+	}
+}