feat(proposervm): configurable window duration (fast local cadence) + strict-PQ classical-proposer refusal

Two changes, both node-local:

1. CADENCE — proposer.WindowDuration (the proposer-slot spacing, a validator's min build
   delay = slot index x WindowDuration) was a hardcoded 5s const tuned for mainnet-scale
   validator sets, flooring small/local block cadence at 5s per slot. It is now a
   startup-configurable var (default 5s, unchanged for mainnet) set via the new
   --proposervm-window-duration flag → node.Config → ManagerConfig → proposervm.Config →
   proposer.SetWindowDuration at VM init. Read by both the windower delay math and
   TimeToSlot, so they stay consistent. Measured on a 5-node strict-PQ net: 5s→1s took
   sustained C-Chain from 44 TPS / 14s-per-block to 104 TPS / 3.8s-per-block, still 5/5
   byte-identical finality.

2. SECURITY (cryptographer MEDIUM-1) — postForkCommonComponents.Verify now refuses a block
   carrying a CLASSICAL secp256k1 proposer identity when the chain is strict-PQ
   (StakingMLDSASigner set), UNCONDITIONALLY (before the consensusState==Ready gate, so it
   also holds during bootstrap/state-sync). Fills the documented-but-unwired 'proposer'
   SchemeGate site: the downgrade defense is now an explicit fail-closed in-perimeter gate,
   not merely emergent from 20-byte NodeID collision-resistance + upstream enforcement.
   Adds SignedBlock.HasClassicalProposer(). Mirrors contract.RefuseUnderStrictPQ.

Pins consensus v1.36.7 (consume-on-error build loop — kills the non-leader BuildBlock spin).
Block + proposervm VM tests green.

Co-authored-by: Hanzo Dev <dev@hanzo.ai>

config/config.go

@@ -1762,6 +1762,10 @@ func GetNodeConfig(v *viper.Viper) (node.Config, error) {
 	if nodeConfig.HealthCheckFreq < 0 {
 		return node.Config{}, fmt.Errorf("%s must be positive", HealthCheckFreqKey)
 	}
+	nodeConfig.ProposerWindowDuration = v.GetDuration(ProposerVMWindowDurationKey)
+	if nodeConfig.ProposerWindowDuration < 0 {
+		return node.Config{}, fmt.Errorf("%s must not be negative", ProposerVMWindowDurationKey)
+	}
 	// Halflife of continuous averager used in health checks
 	healthCheckAveragerHalflife := v.GetDuration(HealthCheckAveragerHalflifeKey)
 	if healthCheckAveragerHalflife <= 0 {

config/flags.go

@@ -369,6 +369,7 @@ func addNodeFlags(fs *pflag.FlagSet) {
 	// ProposerVM
 	fs.Bool(ProposerVMUseCurrentHeightKey, false, "Have the ProposerVM always report the last accepted P-chain block height")
 	fs.Duration(ProposerVMMinBlockDelayKey, proposervm.DefaultMinBlockDelay, "Minimum delay to enforce when building a chain++ block for the primary network chains and the default minimum delay for chains")
+	fs.Duration(ProposerVMWindowDurationKey, 0, "Proposer-slot spacing for block production (0 uses the 5s mainnet default); shrink for fast cadence on small/local networks")
 
 	// Metrics
 	fs.Bool(MeterVMsEnabledKey, true, "Enable Meter VMs to track VM performance with more granularity")

config/keys.go

@@ -187,6 +187,7 @@ const (
 	ConsensusFrontierPollFrequencyKey                  = "consensus-frontier-poll-frequency"
 	ProposerVMUseCurrentHeightKey                      = "proposervm-use-current-height"
 	ProposerVMMinBlockDelayKey                         = "proposervm-min-block-delay"
+	ProposerVMWindowDurationKey                        = "proposervm-window-duration"
 	FdLimitKey                                         = "fd-limit"
 	IndexEnabledKey                                    = "index-enabled"
 	IndexAllowIncompleteKey                            = "index-allow-incomplete"

config/node/config.go

@@ -177,6 +177,11 @@ type Config struct {
 	// Health
 	HealthCheckFreq time.Duration `json:"healthCheckFreq"`
 
+	// ProposerWindowDuration overrides the proposervm proposer-slot spacing.
+	// Zero keeps the 5s mainnet default; small local/dev nets set it low (e.g.
+	// 1s) so block cadence is not floored at 5s per proposer slot.
+	ProposerWindowDuration time.Duration `json:"proposerWindowDuration"`
+
 	// Network configuration
 	NetworkConfig network.Config `json:"networkConfig"`