Delivers catalogue PubSub events to a LiveComponent as send_update/3 refreshes, so a component embedded in ANY host LiveView follows the catalogue live without the host forwarding a single message.

A LiveComponent cannot receive PubSub itself — subscribing from one subscribes the host LiveView process, and every host would then need a handle_info/2 clause for each catalogue event or crash on the first broadcast. The relay is a small process of its own: it holds the subscription, decides which events concern the component (its scope's catalogues), collapses a burst of writes into one refresh, and hands that refresh to the component through Phoenix.LiveView.send_update/3 — the one door into a component that is open from another process.

Lifetime

The relay monitors the host LiveView and exits when it does, and the component stops it (stop/1) when it closes. A component the host unmounted some other way is detected by the ack: each refresh carries a reference the component acknowledges from update/2; a refresh still unacknowledged 15000 ms later means nobody is listening and the relay exits on its own — it does not wait for a second event to notice. (LiveView itself only logs a debug line for a send_update to a component that is gone, so even that one refresh costs nothing visible.)

Events that trigger a refresh

Every {:catalogue_data_changed, kind, uuid, parent} whose parent is one of the component's catalogues, every catalogue-level event (a reorder names only its first row), or any event at all when the component browses without a catalogue restriction — plus the position events (:catalogue_category_reorder, :catalogue_card_refresh, :catalogue_bulk_change) for those catalogues, and every shared-sort change. Events are collapsed with a 250 ms trailing debounce, so one drag that writes a dozen rows refreshes once.