Add explicit routing rules to ping-deacon step:
- WITNESS_PING always goes to deacon/, never to mayor/
- Mayor only receives ALERT messages (Step 3)
- Define what 'healthy' looks like (idle at prompt is normal)
This prevents the witness LLM from misinterpreting the formula
and sending raw WITNESS_PING messages to mayor instead of deacon.
Fixes: gt-uvz90