Deeplink tests

Exact production page: meta refresh 1s + onload deeplink + 500ms store fallback

Exact production Safari 12.3+ page: prod + confirm('Open in App Store?') before fallback

Onload deeplink + 500ms confirm('Open in App Store?') fallback, no meta refresh

Onload deeplink + 6000ms store fallback, no meta refresh

Pre-ed7b327 blur/focus guard: 500ms fallback deferred while blurred/hidden, retried on focus, no meta refresh

Onload deeplink + 3000ms store fallback, no meta refresh

Onload deeplink only, no fallback (does the attempt do anything?)

Buttons only: tap deeplink / tap store (user-gesture baseline)

HTTP 302 straight to the deeplink (legacy direct redirect)