Function record_query_observation 

pub fn record_query_observation(
    observer_did: u64,
    query_subject_hash: u64,
    ts: u64,
) -> NQuin

Record a query event — observer_did queries about query_subject_hash.

The query event hash is derived deterministically from (observer_did, query_subject_hash, ts). Returns 1 quin in EPISTEMIC_CONTEXT so other agents can reference it as a source.

Callers should capture the returned NQuin::object (= query_event_hash) and pass it to assert_inferred_belief for agents who observe this query.