- the purge client's CheckRedirect returns http.ErrUseLastResponse: a 3xx
is logged as a failed purge with its status and the bearer token never
reaches the Location
- cooler.SiteCachePurger moved from the Journal plugin: loopback-only http,
32-character token, 2 s detached request, no token in logs or errors
- NewSiteCachePurgerFor names caller keys (for plugin alias keys)
- PurgeSiteCacheAfterCommit through lagoon.AfterCommit, one POST per save
- SiteCacheFromApp for hooks outside serve; Install publishes the purger
unless a plugin already did, and fails boot on an invalid config
- caching docs section, cooler README, configuration row
