Push Context Events

Push typed, visibility-scoped context for a session (out-of-band from messages).

The engine ingests it into its EXISTING speakable/private fact slots (and proposes memory_candidates to the world model) — NOT raw prompt pass-through. Context is active for its TTL window (default ~10 min) and shapes later replies in this session. speakable_facts may be said; private_facts/forbidden_to_reveal shape the reply but are kept out of it by the leak guard. Idempotent per idempotency_key.