Only the auto-popup was companion-gated — inside the companion WebView
users still saw the 'install the companion' banner in the App Store and
could pop the intro overlay through it. Gates all three paths on
isCompanionApp(): CompanionBanner self-hides, openCompanionIntro() is a
no-op, and the manual-open watcher in CompanionIntroOverlay refuses to
open (the overlay's raw window check also moves to the canonical helper
so there is exactly one detection). No APK change.
