- Add `currentTrainMetadata.ts` to manage carrying forward official position metadata between train snapshots.
- Introduce `lineDisplayName.ts` for mapping line IDs to display names.
- Create `officialPositionCache.ts` for parsing and serializing official position data with cache validation.
- Enhance `officialPositionService.ts` to support persistent caching of official positions and improve resolver functionality.
- Update `requestCoordinator.ts` to allow cancellation of polling requests without disposing of the coordinator.
- Modify `trainTimeFiltering.ts` to incorporate line ID context when checking for duplicate train data.
- Refactor `useCurrentTrain.tsx` to support polling for current train data with official position enrichment.
- Add tests for new features, including persistent cache behavior and handling of ambiguous train data.
harukin-expo-dev-env