S1 Nitro Cache Spike

Use the API endpoints documented in README.md to validate variant-aware caching, middleware ordering, revalidation behavior, and Worker subrequest caching.

• /api/article/123?v=abstract
• /api/article/123?v=full
• /api/debug/article-trace/123?v=abstract
• /api/debug/article-cache-layer/123
• /api/debug/clear-l1/123 (POST)
• /api/debug/revalidate/123?v=abstract
• /api/debug/fetch-tiered?key=article-123
• /api/debug/cache-policy/swr-boolean (S1e)
• /api/debug/cache-policy/swr-stale-max (S1e)