Cardano Updates

  The versionNeedsSnapshot timer fires an empty version-bump snapshot
  after each IncrementTx. When Close is sent before that snapshot
  confirms at the closing node, the node correctly contests with the
  better snapshot, extending the contestation deadline by one
  contestation period (10 * blockTime).

  The previous buffer of 3 * blockTime was too short in that case,
  causing a timeout before ReadyToFanout arrived. Extended to
  13 * blockTime to cover the contest round plus block-latency buffer.

Signed-off-by: Sasha Bogicevic <[email protected]>

Signed-off-by: Sasha Bogicevic <[email protected]>

  When postTx runs async (via asyncTracked), the losing node's
  CollectComTx submission can fail and enqueue PostTxError before
  OnCollectComTx has been observed — leaving the node still in Initial
  state. The existing Open{} guard did not match, causing the wildcard
  PostTxOnChainFailed to fire.

  Fix by adding an Initial{} case mirroring the existing Open{} noop:
  a CollectComTx failure in Initial simply means another party already
  collected the head; OnCollectComTx will arrive shortly.

Signed-off-by: Sasha Bogicevic <[email protected]>

  The SeenSnapshot case in onOpenTimer re-broadcast ReqSn+AckSn on every
  timer tick while waiting for AckSns. With a 5ms timer interval and etcd
  delivering each message back as a NetworkInput, this created a feedback
  loop: each broadcast → etcd echo → resets lastWasTimer → timer fires
  again → more broadcasts → floods the etcd PersistentQueue (capacity 100)
  → blocks processEffects → delays incoming AckSns → exponential slowdown
  (200+ ReqSn per snapshot, 5s+ gaps at snapshot 7+).

  Since etcd guarantees reliable delivery, the retry is unnecessary for
  normal L2 operation. Edge cases (deposit activation, version bumps) are
  handled by CommitFinalized/DecommitFinalized resetting seenSnapshot to
  LastSeenSnapshot, which lets the timer's fresh-send path handle them.

  Restore maybeRequestNextSnapshot in onAckSn so the leader for sn+1
  immediately chains the next snapshot after SnapshotConfirmed, avoiding
  an idle timer interval between snapshots.

Signed-off-by: Sasha Bogicevic <[email protected]>

Signed-off-by: Sasha Bogicevic <[email protected]>

Optimizations applied:
 * Single-pass serialization: each 'TxOut' is serialized once via
   @serialiseData . toBuiltinData@ and reused for both UTxO hash checks
   and accumulator scalar computation.
 * Combined CRS lookup: the reference input for the CRS is looked up once
   and decoded only when the membership check is actually reached.

Apply blake2b_224 before scalar conversion
Compute commitments with the actual CRS used for proofs
Build the accumulator using fanout output order