Add LineUp.deepCopy and use deep copies when importing, snapshotting, restoring, and copying lineUps to avoid shared mutable state. Update StrategyPage.copyWith and StrategyProvider to deep-copy lineUps when constructing strategies. Introduce a _hasLoadedStrategy helper and flushPendingAutosaveBeforeExit in StrategyProvider to attempt a silent autosave (respecting autosave settings) before exit; wire this into unsaved_strategy_guard so it will try to save silently and report failures before showing the dialog. Add comprehensive tests (test/unsaved_strategy_guard_test.dart) to cover autosave-enabled/disabled, no-loaded-strategy, and error cases.