- Recover completed .part files on HTTP 416 without deleting and redownloading
- Add stream stall detection and automatic reconnect for interrupted socket reads
- Implement persistent download state store and pause/resume lifecycle controls
- Add RateLimitCoordinator and ConnectivityGuard circuit breaker for requests
- Support proxy_url configuration and validate aria2 proxy settings
- Add unit tests for 416 recovery, stall reconnect, state store, and network guard
