Keep same-second unread events and bound idle push connections

app/channels/presence_channel.rb

@@ -22,6 +22,6 @@ class PresenceChannel < RoomChannel
     end
 
     def broadcast_read_room
-      ActionCable.server.broadcast "user_#{current_user.id}_reads", { room_id: membership.room_id, at: Time.current.to_fs(:epoch) }
+      ActionCable.server.broadcast "user_#{current_user.id}_reads", { room_id: membership.room_id, at: Time.current.to_f }
     end
 end

app/models/message/broadcasts.rb

@@ -13,7 +13,7 @@ module Message::Broadcasts
   # only the ones who still have it unread or are in it now: by the time this runs,
   # someone may have opened the room and moved on, and would see it marked unread again.
   def broadcast_unread_room
-    payload = ActiveSupport::JSON.encode(roomId: room.id, at: created_at.to_fs(:epoch))
+    payload = ActiveSupport::JSON.encode(roomId: room.id, at: created_at.to_f)
 
     room.memberships.unread.or(room.memberships.connected).pluck(:user_id).each do |user_id|
       ActionCable.server.broadcast UnreadRoomsChannel.stream_name_for(user_id), payload, coder: nil