Sub-ticket of MARS-339 PWA install-prompt (A2HS offer): mobile-only, only when not already installed, dismissible. Android/Chrome=capture beforeinstallprompt→custom 'Instalar app' button/banner→prompt(); iOS Safari=manual 'Compartir→Agregar a inicio' instructions banner (no auto-prompt API). Builds on MARS-338 PWA infra. Cross-fleet Elazar directive (Pluto=PLUTO-443). · mars