test(consensus): add automated regression test suite for validator consensus failure modes (closes #199)

[guptakumarranjeet150]

Summary of Changes

Resolves #199.

This PR implements an end-to-end automated regression test suite verifying validator consensus safety, liveness, and recovery bounds across adversarial failure modes.

Key Architectural & Test Enhancements

1. Network Partition & Healing Recovery:

   • Tests clean two-way split-brain network partition (testCleanNetworkPartitionBlocksConsensus) asserting zero quorum can be reached during disconnected states.
   • Tests partition healing (testHealedNetworkPartitionRecoversLiveness) asserting immediate convergence and consensus resumption within bounded rounds.

2. Byzantine Equivocation Resilience:

   • Tests conflicting proposal broadcasts (testByzantineEquivocationResilience) verifying honest 2/3+ majority converges safely under $F < N/3$ threshold.

3. Validator Crash & Timeout Faults:

   • Tests non-responsive validators (testValidatorTimeoutFaultAndRecovery) ensuring protocol liveness and recovery under bounded offline duration.

4. Network Delay & Jitter Injection:

   • Tests probabilistic message delay and jitter latency bounds (testMessageDelayAndJitterBounds).

5. Dynamic 2/3+ Quorum Threshold & Vote Invariance:

   • Verifies threshold calculation formula $\lfloor 2N/3 \rfloor + 1$ across cluster sizes from 1 to 100 nodes (testQuorumThresholdCalculations).
   • Verifies duplicate vote deduplication and unregistered validator rejection (testDuplicateAndIneligibleApprovalFiltering).

6. Core Engine Consistency:

   • Fixed proposal alignment in src/consensus-sim/simulation.ts so honest validators vote on canonical round block proposals.
   • Added tests/consensus_sim.test.ts for the npm run test:consensus-sim target.

Verification

• node tests/consensus/validator_failure_modes.test.cjs -> All 7 tests PASSED.
• node scripts/validate-ci-workflow.cjs -> PASSED.
• node scripts/validate-docker-cache-config.cjs -> PASSED.