v1.3.3 — DAG-based view change + deterministic gas limit

DAG-based view change + deterministic gas limit

Follows up on v1.3.1 (four-way fork fix) by eliminating the last two sources
of cross-validator non-determinism observed on the 4-validator testnet:

1. View change triggers are now DAG-based, not wall-clock based.
   Both checkLeaderTimeoutLocked and checkInsufficientSupportTimeoutLocked
   now fire when the local DAG has advanced past the leader round by a fixed
   round count (8 and 12 rounds respectively), not after N milliseconds of
   elapsed wall clock. Because the DAG converges via gossip, all validators
   reach the decision point at the same logical moment. Previously, validator
   A's timer could fire for wave W while B was still committing W normally,
   giving them divergent committed sequences.

2. Block gas limit is now inherited verbatim from the parent block.
   Previously the block header used nt.dynamicScaler.GetCurrentGasLimit(),
   which adjusts based on locally-observed TPS and therefore differs per
   validator. Observed at block 254 on testnet: val-1 produced
   gasLimit=30,180,000 while val-4 produced 30,000,000 for the same commit.
   Every other header field matched; only gasLimit differed. Now every
   validator uses parentBlock.Header.GasLimit, which is identical across
   nodes. Dynamic scaling still tracks its internal target for metering, but
   header-visible changes need a deterministic epoch mechanism (future work).

Testnet verification

All 4 validators on the Digital Ocean testnet now produce identical block
hashes past block 254 (previous divergence point) — the chain stays in
consensus indefinitely with the full determinism pipeline in place.

Upgrade notes

Chain data MUST be wiped on upgrade.