Balance/history now render as soon as tx downloads finish instead of
blocking on every historical Merkle proof, critical for mobile where
proof-checking can take much longer than the download itself. Proofs
continue to be checked in the background and each tx's Verified flag
catches up progressively; header ranges are now fetched in batches
(blockchain.block.headers) instead of one call per header to keep this
fast over high-latency links.
Coin selection (UtxoSpendability.IsSpendable) refuses to spend a UTXO
until its Merkle proof is actually checked, regardless of confirmation
count, so a server that fabricates a confirmed balance can get it
displayed early but never spent before the forgery is caught. The disk
cache only ever persists the fully-verified end state of a sync.
UI surfaces the new PendingVerificationSats/SpendableSats split with a
"verifying..." badge, and the sync save now runs off the UI thread to
avoid freezing on slower hardware.
The password parameter accepts null, which saves the wallet in plaintext.
The XML doc comment now makes explicit that this is only acceptable when
the user has explicitly opted out of encryption with a UI warning shown.
davide