Wires dirties_on into a global change, so ordinary Ash writes trigger the cascade with no host boilerplate.

A global change (rather than one added per action) means actions declared later are covered too — the point of the feature is that no write site can be forgotten, and a per-action wiring would reintroduce exactly that risk.

The key derivation is resolved HERE, at compile time, and passed as options: the change then does no introspection per write.