Advanced AI Prompt for Lambda@Edge Security Header Injection

Act as a Cloud Security Architect. Design a highly optimized AWS Lambda@Edge function triggered on the 'Viewer Response' event for the [CLOUDFRONT_DIST] distribution. The function must programmatically inject dynamic HTTP security headers to achieve an A+ Mozilla Observatory score. Enforce a strict Content-Security-Policy (CSP) utilizing [CSP_RULES], mandate HTTP Strict Transport Security (HSTS) with a [HSTS_MAX_AGE], and inject X-Frame-Options to completely prevent clickjacking. Write the Node.js logic to ensure existing headers from the origin are not destructively overwritten unless they violate the new strict security baseline.