Skip the unread notice for members who have caught up

Now that the unread fanout runs in a job, it can run after a member has
already opened the room and moved on to another one. Their sidebar would
then mark the room unread for a message they have seen.

The job now notifies only members who still have the room unread or are
in it now. Room#receive marks members who aren't in the room unread, and
opening the room clears it, so a member who caught up in the meantime is
skipped. When the
job runs right away this is the same set of people as before, except
members who have hidden the room, whose sidebar doesn't list it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JVFo3Lt9T8M5NR7KxVvsZ2

app/models/message/broadcasts.rb

@@ -9,11 +9,13 @@ module Message::Broadcasts
   end
 
   # Fanned out to the room's members rather than published on one global stream, so
-  # that the timing of activity in a room only reaches people who are in it.
+  # that the timing of activity in a room only reaches people who are in it. Of those,
+  # 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)
 
-    room.memberships.pluck(:user_id).each do |user_id|
+    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
     end
   end

test/controllers/messages_controller_test.rb

@@ -58,6 +58,8 @@ class MessagesControllerTest < ActionDispatch::IntegrationTest
   end
 
   test "creating a message broadcasts unread room to each member" do
+    memberships(:david_watercooler).present # the poster is in the room
+
     @room.users.each do |member|
       assert_broadcasts UnreadRoomsChannel.stream_name_for(member.id), 1 do
         perform_enqueued_jobs only: Message::BroadcastUnreadRoomJob do
@@ -77,6 +79,20 @@ class MessagesControllerTest < ActionDispatch::IntegrationTest
     assert_enqueued_with job: Message::BroadcastUnreadRoomJob, args: [ Message.last ]
   end
 
+  test "the unread fanout skips a member who has opened the room since" do
+    membership = memberships(:jason_watercooler)
+
+    post room_messages_url(@room, format: :turbo_stream), params: { message: { body: "New one", client_message_id: 999 } }
+    assert membership.reload.unread?
+
+    membership.present
+    membership.reload.disconnected
+
+    assert_no_broadcasts UnreadRoomsChannel.stream_name_for(membership.user_id) do
+      perform_enqueued_jobs only: Message::BroadcastUnreadRoomJob
+    end
+  end
+
   test "creating a message doesn't broadcast unread room to non-members" do
     outsiders = User.where.not(id: @room.users.map(&:id))
     assert outsiders.any?, "need someone outside the room for this test to mean anything"