fix: preserve schema 15 compatibility for v0.1.8

tests/test_month_settlement_schema.py

@@ -43,16 +43,22 @@ def test_migration_is_idempotent_and_preserves_legacy_drafts(tmp_path):
         assert conn.execute("SELECT COUNT(*) FROM monthly_settlement").fetchone()[0] == 0
 
 
-def test_schema15_upgrade_drops_only_latest_run_id_and_preserves_closed_row(tmp_path):
+def test_schema15_upgrade_removes_schema16_run_link_and_preserves_rows(tmp_path):
     path = str(tmp_path / "schema15.sqlite3")
     init_db(path)
     with sqlite3.connect(path) as conn:
+        conn.execute("INSERT INTO asset_snapshot_runs(id,basis_date,close_status,created_at) VALUES('run-1','2026-09-30','complete_exact','t')")
         conn.execute("ALTER TABLE monthly_settlement ADD COLUMN latest_run_id TEXT REFERENCES asset_snapshot_runs(id) ON DELETE RESTRICT")
         conn.execute("UPDATE schema_meta SET value='15' WHERE key='schema_version'")
         conn.execute("""INSERT INTO monthly_settlement
             (id,month,basis_date,status,version,created_by,created_at,updated_by,updated_at,
              approved_by,approved_at,approved_version,approved_fingerprint,closed_by,closed_at,latest_run_id)
             VALUES ('m1','2026-09','2026-09-30','closed',2,'u','t','u','t','r','t',1,'fp','c','t','run-1')""")
+        conn.execute(
+            """INSERT INTO account_snapshot
+               (id,basis_date,source_type,source_id,name,amount,monthly_settlement_id,created_at)
+               VALUES ('snapshot-1','2026-09-30','account','account-1','Main',100,'m1','t')"""
+        )
         before = conn.execute("SELECT id,month,basis_date,status,version,memo,approved_by,closed_by FROM monthly_settlement").fetchall()
     init_db(path)
     init_db(path)
@@ -60,7 +66,15 @@ def test_schema15_upgrade_drops_only_latest_run_id_and_preserves_closed_row(tmp_
         assert conn.execute("SELECT value FROM schema_meta WHERE key='schema_version'").fetchone()[0] == "15"
         assert conn.execute("SELECT id,month,basis_date,status,version,memo,approved_by,closed_by FROM monthly_settlement").fetchall() == before
         assert "latest_run_id" not in {row[1] for row in conn.execute("PRAGMA table_info(monthly_settlement)")}
-        assert conn.execute("PRAGMA foreign_key_list(monthly_settlement)").fetchall() == []
+        assert conn.execute("SELECT id FROM asset_snapshot_runs").fetchall() == [("run-1",)]
+        assert conn.execute("SELECT id,monthly_settlement_id FROM account_snapshot").fetchall() == [("snapshot-1", "m1")]
+        assert conn.execute("PRAGMA foreign_key_check").fetchall() == []
+        migrated_shape = [row[1:] for row in conn.execute("PRAGMA table_info(monthly_settlement)")]
+    canonical_path = str(tmp_path / "canonical.sqlite3")
+    init_db(canonical_path)
+    with sqlite3.connect(canonical_path) as conn:
+        canonical_shape = [row[1:] for row in conn.execute("PRAGMA table_info(monthly_settlement)")]
+    assert migrated_shape == canonical_shape
 
 
 @pytest.mark.parametrize("column,value", [("month", "2026-13"), ("month", "202609"), ("basis_date", "2026-02-30"), ("version", 0)])