feat: transmit cache keys on room channel subscribe

app/channels/room_channel.rb

@@ -7,6 +7,7 @@ class RoomChannel < ApplicationCable::Channel
     ensure_stream
     update_subscription
     broadcast_presence
+    transmit_cache_keys
   end
 
   def update_presence
@@ -24,6 +25,19 @@ class RoomChannel < ApplicationCable::Channel
     ActionCable.server.broadcast(pubsub_token, { event: 'presence.update', data: data })
   end
 
+  # Push the authoritative cache-key map to this subscriber on every
+  # (re)subscribe. Boot and reconnect cache freshness ride the same
+  # account.cache_invalidated event the dashboard already handles for live
+  # invalidations — the client never pulls /cache_keys itself.
+  def transmit_cache_keys
+    return if @current_account.blank? || !@current_user.is_a?(User)
+
+    transmit({
+               event: Events::Types::ACCOUNT_CACHE_INVALIDATED,
+               data: { account_id: @current_account.id, cache_keys: @current_account.cache_keys }
+             })
+  end
+
   def ensure_stream
     stream_from pubsub_token
     stream_from "account_#{@current_account.id}" if @current_account.present? && @current_user.is_a?(User)

spec/channels/room_channel_spec.rb

@@ -21,4 +21,19 @@ RSpec.describe RoomChannel do
     expect(subscription).to have_stream_for(user.pubsub_token)
     expect(subscription).to have_stream_for("account_#{account.id}")
   end
+
+  it 'transmits the account cache keys to user subscribers' do
+    subscribe(user_id: user.id, pubsub_token: user.pubsub_token, account_id: account.id)
+
+    cache_event = transmissions.find { |message| message['event'] == 'account.cache_invalidated' }
+    expect(cache_event['data']['account_id']).to eq(account.id)
+    expect(cache_event['data']['cache_keys'].keys).to match_array(%w[label inbox team])
+  end
+
+  it 'does not transmit cache keys to contact subscribers' do
+    subscribe(pubsub_token: contact_inbox.pubsub_token)
+
+    cache_event = transmissions.find { |message| message['event'] == 'account.cache_invalidated' }
+    expect(cache_event).to be_nil
+  end
 end