Tool-result error state was an in-memory-only message key, lost on reload. Add an
is_error column to conversations (migration 060, backfilled False) and thread it through
the four save layers (memory facade → StorageBackend protocol → SQLite + PostgreSQL):
save_message/save_messages_bulk persist it, reconstruct_messages emits it on tool rows,
and the session tool-result + synthetic-cancel saves + the fork bulk-copy pass it. It
rides as the last conversations column so reconstruct's row-tuple positions stay stable
(legacy fixtures default False). history_decoration already prefers the persisted flag
over its text heuristic, so reload fidelity improves immediately.
First sub-commit of the canonical-trajectory storage cut (folds into rev 060).
Patrick Buckley