Yuanbao's recall feature was reading the gateway JSONL directly to look up
messages by platform message_id, which state.db does not preserve. Migrated
to use load_transcript() which returns DB messages.
Recall branch A1 (message_id match) now falls through to A2 (content match)
or B (system note) for all sessions — a documented degradation. Follow-up
issue: add platform_message_id column to state.db messages to restore
exact-id matching.
