WalletSynchronizer now pipelines JSON-RPC requests (address subscribes,
histories, tx downloads and Merkle proofs run in parallel batches) and
keeps per-connection caches of downloaded transactions and verified
proofs, so notification-triggered resyncs only cost the delta.
The app connects automatically when a wallet opens, keeps one
synchronizer per connection, and queues notifications that arrive
during a sync instead of dropping them: incoming transactions now show
up within seconds.
davide