The plugin hasn't been checked with JavaScript turned off #823

#550's no-JS criterion is unchecked, and since presence is recorded through Heartbeat, most of it can't work without JavaScript; the question is whether everything else keeps working.

Without JS, Heartbeat never runs, so someone shows as online only for one TTL (150 seconds) after logging in (lifecycle.php), and nothing refreshes. Post locks still work, since core's post.php sets the lock on load and post-lock-bridge.php stores it. The block editor needs JS anyway, so the synced pattern indicator is out of scope.

Tasks

• Load each screen the plugin touches with JS off and check nothing breaks or shows stale data as current
• Check post locks still stop a second editor
• Check the settings page saves
• Write down on 📌 Tracking: Presence API path to Core #550 what's expected not to work without JS, and why

Part of #550.