fix: hide spent rescue to prevent StateError crash; log per-attempt starts

Expose engine.rescueUsed getter and surface it through GameViewState so
the result overlay can omit the watch-ad FilledButton after a rescue has
been consumed, preventing a second tap from calling useContinue /
addExtraMoves and hitting their StateError guard. Give-up is promoted to
FilledButton when rescue is unavailable for clear affordance.

Also emit stageStart / endlessStart analytics in restart() so every
attempt (not just the first) is bracketed by a matching start event.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/game/engine/game_engine.dart

@@ -82,6 +82,7 @@ class GameEngine {
   List<Objective> get objectives => List.unmodifiable(_objectives);
   GamePhase get phase => _phase;
   StuckReason? get stuckReason => _stuckReason;
+  bool get rescueUsed => _rescueUsed;
 
   int get starsEarned => _phase == GamePhase.won
       ? _stage.stars.starsFor(movesLeft: movesLeft)