Opt-in 10s FastCGI/proxy micro-cache per site (migration 053) with safe
bypasses for logged-in/admin/cart cookies and paths, X-SK-Cache header
for verification, and a shared-zone purge. Flows through the drift-safe
vhost render seam so detection and writes always agree.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
