MCP: Node binary

[xinyuan-dev]

This PR implements a simple node binary for MCP for testing.

• The Node runs three tasks simultaneously (using tokio::spawn):
  • CadenceTask runs cadence state machine and bridges cadence events
  • DATask runs da state machine and bridges its events
  • ProposingTask runs a mock proposing state machine, that emits proposals when polled
• The Node tracks timers internally, using tokio's DelayQueue.
• The Node talks to a NetworkHandle to sends/receives one of three variants of networking messages (pre-serialized):
  • Cadence
  • Chunk
  • ChunkRequest
  • (all network messages must be authenticated by networking adaptor)
• A Node is constructed solely from a NodeConfig, deserialized from a toml config, that contains all parameters of the chain and the node itself
• Stubbed components
  • types: node id/pub key/etc still uses the small stub types
  • udp network: packet is just [sender(8), variant(1), payload] over udp. packets larger than mtu is dropped.
  • proposing logic: propose random bytes of random length 1B-1MiB, proposed at slot deadlines - C
  • proposer election: simple rotating seats
  • finalization: only logging

The monad-mcp-node crate includes two binaries:

• monad-mcp-node: $0 <config.toml> runs a standalone node
  • monad-mcp-node/swarm.sh <n_val> <m_sec> runs a swarm using the standalone node as processes
• examples/swarm: $0 <n_val> <m_sec> runs a swarm of n validators for m seconds in the same process, communicating through real network (loopback interface)

The code is mostly generated using Claude Fable 5.1 and GPT 6.