feat(monitoring): add cross-node consistency probe for split-state detection

[liu971227-sys]

Summary

• add node/consensus_probe.py to compare /health, /epoch, /api/stats, and /api/miners across nodes
• return machine-readable JSON report and non-zero exit code on divergence
• add unit tests for divergence detection and snapshot collection
• document usage in monitoring/README.md

Why

This is a hardening follow-up for bounty #58 (cross-node consensus attacks): operators need an automated probe that detects split-state/replication divergence before clients trust inconsistent node reads.

Validation

• python -m py_compile node/consensus_probe.py
• python -m pytest tests/test_consensus_probe.py -q

Related bounty issue:

• [BOUNTY] 🔴 Red Team: Cross-Node Consensus Attacks (100 RTC) rustchain-bounties#58

[liu971227-sys]

Review Tier Label Gate will require a BCOS tier label on this non-doc PR.

Given this is operational consensus/replication hardening tooling, BCOS-L1 seems appropriate.

Could a maintainer add BCOS-L1 (or bcos:l1) and re-run checks?