Patch over v1.3.0. User-facing fix is the HighScores crash on Android
that hit users when MODE_OPTIONS grew to 5 but the screen's local arrays
stayed at length 4. The web build itself wasn't affected by that crash
but rebuilds anyway to pick up: bounds-clamping on stored prefs indexes,
the BackgroundRunner abstraction that restored html:dist after months of
silent breakage (Thread/Runtime/String.format calls had crept into
shared core), and the GwtAdManager dead-method cleanup.