Companion

30s grace after backgrounding (survives brief app-switches).

30 minutes: the longest the decrypted seed may live while backgrounded before the hold-aware lifetime ceiling (#276) wipes an idle, unheld session. A held op / Kicks match defers it. Long enough not to disrupt a quick app-switch or a backgrounded match; short enough that a forgotten, backgrounded app doesn't hold the seed in memory all day.

5 minutes of foreground inactivity.

Resolve the singleton SessionLock and register its app-level hooks. Call once from the host Application.onCreate. Foreground idle still needs each Activity to forward onUserInteraction() → onUserActivity.