Adds the listener-side state for the live-chat panel (T1 #2):
AudioRoomViewModel.chat: StateFlow<List<LiveActivitiesChatMessageEvent>>
AudioRoomViewModel.onChatEvent(event)
Same precedent as `presences` — the platform layer is the source
(amethyst observes LocalCache for kind=1311 + #a=[roomATag] and
pipes events here). The list is `created_at`-ascending so the chat
panel auto-scrolls newest at the bottom. Dedupes by event id so a
relay re-emit on reconnect doesn't double up the transcript.
Tests:
* onChatEventAccumulatesMessagesSortedByCreatedAt — out-of-order
arrivals end up in the right place on screen
* onChatEventDedupesByEventId — same event from two relays /
one reconnect produces ONE row
The amethyst-side wire sub + chat panel UI come next.
Claude
25a8c460aa