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- Clean up outdated file references and duplicate assets

DEVELOPMENT_QUICKSTART.md

@@ -0,0 +1,39 @@
+# Insertr Development Quickstart
+
+## Project Structure
+
+- `lib/` - JavaScript library development (all Node.js tooling)
+- `insertr-cli/` - Go CLI application  
+- `demo-site/` - Static HTML demo site
+
+## Getting Started
+
+### Library Development
+```bash
+cd lib/
+npm install
+npm run serve    # Start development server
+npm run check    # Validate setup
+npm run demo     # Show demo instructions
+```
+
+### CLI Development  
+```bash
+cd insertr-cli/
+air             # Hot reload development server
+```
+
+### Build Everything
+```bash
+cd lib/
+npm run build:all   # Builds library + CLI with embedded assets
+```
+
+## Architecture
+
+The CLI embeds the JavaScript library at build time for distribution. During development:
+- `lib/` contains the JavaScript library source and build tools
+- Air (Go hot reload) watches `lib/src/` and rebuilds when library changes
+- Demo site served from `lib/` package for unified development experience
+
+All Node.js dependencies and scripts are now consolidated in the `lib/` package.