gui-update is a plain function, so it cannot wait. It returns the work to do
as values. A command is an (Event %m), synced in a fiber of its own, whose
answer is the next message. A subscription is a source of messages that the
model asks for: after each update the app starts the new ones and cancels the
ones that are gone, by key. every sends a message on a timer, and
subscription takes a source of one's own.
The fibers belong to the app's scope and post their messages to the UI
thread, so gui-update and view only run there. Closing the window cancels
them. The prelude's path macros already use the name update, hence
gui-update.
🤖 Generated with [ECA](https://eca.dev) (anthropic/claude-opus-4-8)
Co-Authored-By: eca-agent <git@eca.dev>
