Use multiplatform-settings for cross-platform persistence. Character
auto-loads from storage on launch (falls back to EXAMPLE_CHARACTER).
Auto-saves on every change with 500ms debounce via viewModelScope.
Uses DataLoader.serialize/deserialize for JSON conversion. Works on
all platform targets (Android, Desktop, Web, iOS).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>