Drops cached palette-card previews when the component they drew has been recompiled.

A preview is markup produced by a component's module. Recompile the module and the markup can change — and a stale one is the worst kind of wrong, because it looks fine: the author sees the component they edited still drawn the old way and concludes their edit did not take.

Hung off runtime:after_module_compile, which the compiler already announces, rather than a call wired into the compiler by hand. The core is a participant in its own events (ADR-14), so this is the same mechanism an extension would use to react to the same fact — see MishkaCmsCore.Builder.Events.

It cannot tell WHICH site's previews a module belongs to without loading it, so it drops all of them. That is the cheap and correct trade: the cache refills at about two milliseconds an entry, and a compile is rare next to a hover.