v2.18.1 — Migration safety fix (spec-214 backward compat)

v2.18.1 (2026-09-07)

Fix: spec-214 migration safety and backward compatibility for pre-214 clusters

Three bugs introduced by spec-214 that break any cluster that has not yet run
initialize_schema() after upgrading:

• add_graph_id_to_nodes was destructive by default: Steps 4–7 (DROP TABLE +
  RENAME) ran automatically on every initialize_schema() call when the compound PK
  didn't exist, destroying data if RENAME TABLE failed (IRIS syntax is
  ALTER TABLE old RENAME new, not RENAME TABLE x TO y). The table-recreation path
  is now gated behind recreate_pk=True and is never called from the normal migration
  path. The default is additive-only: add column, migrate data.
• create_node always referenced graph_id: INSERT INTO nodes (node_id, graph_id)
  failed on any pre-214 schema. The engine now probes for the column at init time
  (_probe_nodes_graph_id) and emits a compatible INSERT on older schemas.
• bulk_create_nodes had wrong param count: The bulk node template had 4 params but
  the caller passed 2. Fixed to 3 params for the post-214 path (nodes_with_graph
  template) and 2 params for the pre-214 fallback.