refactor: implement script tag approach for library inclusion

- Add script tags to demo-site HTML files for manual development
- Disable CLI inline script injection to prevent duplicate scripts
- Add library serving endpoints to servedev command
- Update build process to auto-copy library to demo-site
- Add CDN URL helpers for future production deployment
- Update .gitignore for generated demo-site files

Fixes .insertr-gate authentication for manual npm run serve workflow
while maintaining clean separation between CLI and manual setups.

insertr-cli/cmd/servedev.go

@@ -80,6 +80,12 @@ func runServedev(cmd *cobra.Command, args []string) {
 		serveEditorAsset(w, r, assetPath)
 	})
 
+	// Handle insertr library files
+	http.HandleFunc("/insertr/", func(w http.ResponseWriter, r *http.Request) {
+		assetPath := strings.TrimPrefix(r.URL.Path, "/insertr/")
+		serveLibraryAsset(w, r, assetPath)
+	})
+
 	// Handle all other requests with our enhanced file server
 	http.Handle("/", fileServer)
 
@@ -120,6 +126,24 @@ func serveEditorAsset(w http.ResponseWriter, r *http.Request, assetPath string)
 	http.ServeFile(w, r, assetFile)
 }
 
+// serveLibraryAsset serves the insertr library files from embedded assets
+func serveLibraryAsset(w http.ResponseWriter, r *http.Request, assetPath string) {
+	w.Header().Set("Content-Type", "application/javascript")
+
+	var script string
+	switch assetPath {
+	case "insertr.js":
+		script = content.GetLibraryScript(false)
+	case "insertr.min.js":
+		script = content.GetLibraryScript(true)
+	default:
+		http.NotFound(w, r)
+		return
+	}
+
+	w.Write([]byte(script))
+}
+
 // enhancedFileSystem wraps http.FileSystem to provide enhanced HTML serving
 type enhancedFileSystem struct {
 	fs       http.FileSystem