qkc/slave 07: add SlaveComm runtime and Python interop validation

[iteyelmp]

Summary

Final PR in the Slave migration series.

Add SlaveComm runtime integrating:

• MasterConn
• PeerConn
• XshardConn
• XshardPool

Add real Python interoperability validation using a pyquarkchain
process over TCP.

Changes

• Add SlaveComm lifecycle management
• Wire all cluster communication components together
• Add real Python Master interoperability tests

Testing

Unit tests:

• connection lifecycle
• RPC dispatch
• peer routing
• xshard communication
• cleanup handling

Real Python Master integration tests:

1. Master bootstrap flow

• Start real pyquarkchain Master
• Connect Go Slaves
• Verify Master → Slave PING/PONG
• Verify CONNECT_TO_SLAVES_REQUEST creates xshard connections
• Verify slave communication bootstrap completes successfully

2. Peer lifecycle flow

• Connect external peer through Master SimpleNetwork
• Verify CREATE_CLUSTER_PEER_CONNECTION_REQUEST creates PeerConn
• Verify Dispatcher peer registration
• Disconnect peer
• Verify DESTROY_CLUSTER_PEER_CONNECTION_COMMAND removes PeerConn

All tests pass.