refactor: consolidate all Node.js development into lib package

- Move scripts/ to lib/scripts/ and convert to ESM modules
- Consolidate dependencies: add live-server to lib/package.json
- Remove root package.json and node_modules split
- Preserve CLI integration via existing rebuild-library.sh
- Add development quickstart guide for new unified workflow
- Clean up outdated file references and duplicate assets

insertr-cli/pkg/content/injector.go

@@ -126,11 +126,11 @@ func (i *Injector) injectLinkContent(node *html.Node, content string) {
 	i.injectTextContent(node, content)
 }
 
-// addContentAttributes adds necessary data attributes for editor functionality
+// addContentAttributes adds necessary data attributes and insertr class for editor functionality
 func (i *Injector) addContentAttributes(node *html.Node, contentID string, contentType string) {
 	i.setAttribute(node, "data-content-id", contentID)
 	i.setAttribute(node, "data-content-type", contentType)
-	i.setAttribute(node, "data-insertr-enhanced", "true")
+	i.addClass(node, "insertr")
 }
 
 // InjectEditorAssets adds editor JavaScript and CSS to HTML document
@@ -193,6 +193,48 @@ func (i *Injector) setAttribute(node *html.Node, key, value string) {
 	})
 }
 
+// addClass safely adds a class to an HTML node
+func (i *Injector) addClass(node *html.Node, className string) {
+	var classAttr *html.Attribute
+	var classIndex int = -1
+
+	// Find existing class attribute
+	for idx, attr := range node.Attr {
+		if attr.Key == "class" {
+			classAttr = &attr
+			classIndex = idx
+			break
+		}
+	}
+
+	var classes []string
+	if classAttr != nil {
+		classes = strings.Fields(classAttr.Val)
+	}
+
+	// Check if class already exists
+	for _, class := range classes {
+		if class == className {
+			return // Class already exists
+		}
+	}
+
+	// Add new class
+	classes = append(classes, className)
+	newClassValue := strings.Join(classes, " ")
+
+	if classIndex >= 0 {
+		// Update existing class attribute
+		node.Attr[classIndex].Val = newClassValue
+	} else {
+		// Add new class attribute
+		node.Attr = append(node.Attr, html.Attribute{
+			Key: "class",
+			Val: newClassValue,
+		})
+	}
+}
+
 // Element represents a parsed HTML element with metadata
 type Element struct {
 	Node    *html.Node