- Embed DownloadQueueLookup into DownloadQueueState; add updatedForIndices() for O(changed) incremental updates during frequent progress ticks instead of full O(n) rebuild
- downloadQueueLookupProvider now reads pre-computed lookup from state directly
- Replace sync file deletion in DownloadedEmbeddedCoverResolver with unawaited async cleanup to avoid blocking the main thread
- Parse JSON payloads on iOS native side (parseJsonPayload) so event sinks and method channel responses return native objects, avoiding redundant Dart-side JSON decode
- Use .cast<String, dynamic>() instead of Map.from() in _decodeMapResult for zero-copy map handling