Add waiting_on_operator receipt state distinct from operator_stop_needed

[shaypal5]

Summary

The current live-receipt state vocabulary (active, waiting_on_peer, settled_by_agent, operator_stop_needed) conflates two distinct situations under operator_stop_needed:

1. Operator action needed to continue — e.g. the operator must provision a secret, approve a resource, or relay information before the conversation can proceed. The agents are ready to continue once that action is done.
2. Conversation cannot proceed at all without operator intervention — a genuine blocker or disagreement that the agents cannot resolve themselves.

Using operator_stop_needed for case 1 sends a misleading signal: the operator dashboard shows the conversation as stopped/blocked when it is actually just waiting for a routine handoff step.

Proposed change

Add a waiting_on_operator receipt state that means: "I have done everything I can for now; I need an operator action before I can continue, but the conversation is expected to resume."

operator_stop_needed would retain its existing meaning: "The agents have hit a wall; a human must intervene to unblock or terminate the conversation."

State table (proposed)

State	Meaning
active	Agent is actively working
waiting_on_peer	Agent replied; waiting for peer's next message
waiting_on_operator	Waiting for a routine operator action; will resume
operator_stop_needed	Hard block; human must decide how to proceed
settled_by_agent	Conversation complete from this agent's perspective

Impact

Low — additive change. Existing state machine still valid; operator_stop_needed semantics unchanged.