Keep an unread notice older than the latest read from marking the room

The job picks the room's members once and then publishes to them one at a
time, as the request did before it. A member who opens the room during that
loop gets the read event in their other tabs and then the older notice,
which marked the room unread again. Both events now carry the server time,
and the sidebar ignores a notice dated before the room's latest read. The
notice still moves a direct room to the top.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0142qgjggdJ2KDdGk7RF9Xm9

app/javascript/controllers/read_rooms_controller.js

@@ -16,7 +16,7 @@ export default class extends Controller {
     })
   }
 
-  #read = ({ room_id }) => {
-    this.dispatch("read", { detail: { roomId: room_id } })
+  #read = ({ room_id, at }) => {
+    this.dispatch("read", { detail: { roomId: room_id, at } })
   }
 }