New MeshPeer.msg (1 Hz DDS heartbeat: robot_id, social_state, active persons,
greeted names) and MeshHandoff.msg (person context transfer on STATE_LEAVING).
mesh_comms_node subscribes to person_states and orchestrator/state, publishes
announce heartbeat, triggers handoff on LEAVING, tracks peers with timeout
cleanup, and propagates mesh-wide greeting deduplication via /social/mesh/greeted.
73/73 tests passing.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>