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- Clean up outdated file references and duplicate assets

lib/src/core/editor.js

@@ -130,7 +130,7 @@ export class InsertrEditor {
                 background-color: rgba(0, 124, 186, 0.05) !important;
             }
             
-            [data-insertr-enhanced="true"]:hover::after {
+            .insertr:hover::after {
                 content: "✏️ " attr(data-content-type);
                 position: absolute;
                 top: -25px;