8. Install Prompt

The install banner is built around the beforeinstallprompt browser event. The plugin:

1. Listens for beforeinstallprompt and stores the event (deferred).
2. Shows the banner according to the configured trigger type.
3. On Install click, calls deferredPrompt.prompt() and waits for user choice.
4. On appinstalled, fires a beacon event.

For iOS Safari (which does not fire beforeinstallprompt), the iOS overlay shows share-button instructions.

Dismiss persistence: Dismissal is stored in localStorage with a timestamp. The banner will not show again until dismiss_days have elapsed.