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/pkg/content/library.go

@@ -2,6 +2,7 @@ package content
 
 import (
 	_ "embed"
+	"fmt"
 )
 
 // Embedded library assets
@@ -24,3 +25,26 @@ func GetLibraryScript(minified bool) string {
 func GetLibraryVersion() string {
 	return "1.0.0"
 }
+
+// GetLibraryURL returns the appropriate library URL for script injection
+func GetLibraryURL(minified bool, isDevelopment bool) string {
+	if isDevelopment {
+		// Local development URLs - relative to served content
+		if minified {
+			return "/insertr/insertr.min.js"
+		}
+		return "/insertr/insertr.js"
+	}
+
+	// Production URLs - use CDN
+	return GetLibraryCDNURL(minified)
+}
+
+// GetLibraryCDNURL returns the CDN URL for production use
+func GetLibraryCDNURL(minified bool) string {
+	version := GetLibraryVersion()
+	if minified {
+		return fmt.Sprintf("https://cdn.jsdelivr.net/npm/@insertr/lib@%s/dist/insertr.min.js", version)
+	}
+	return fmt.Sprintf("https://cdn.jsdelivr.net/npm/@insertr/lib@%s/dist/insertr.js", version)
+}