feat: support durable task cancellation without foreign keys

internal/storage/mysql/migrate.go

@@ -183,8 +183,7 @@ func Status(ctx context.Context, db *sql.DB) ([]MigrationStatus, error) {
 	return result, rows.Err()
 }
 
-// CheckSchema rejects missing, modified, dirty and unexpected versions. It does
-// not execute DDL. A matched migration ledger is not proof against manual DDL drift.
+// CheckSchema 校验迁移记录并禁止外键，不执行 DDL；不代表已核验其他手工结构漂移。
 func CheckSchema(ctx context.Context, db *sql.DB) error {
 	wanted, err := Migrations()
 	if err != nil {
@@ -203,5 +202,12 @@ func CheckSchema(ctx context.Context, db *sql.DB) error {
 			return errors.New("schema is dirty or does not match this binary")
 		}
 	}
+	var foreignKeys int
+	if err := db.QueryRowContext(ctx, `SELECT COUNT(*) FROM information_schema.REFERENTIAL_CONSTRAINTS WHERE CONSTRAINT_SCHEMA=DATABASE() AND LEFT(TABLE_NAME,6) IN ('orbit_','pulse_','weave_')`).Scan(&foreignKeys); err != nil {
+		return err
+	}
+	if foreignKeys != 0 {
+		return errors.New("foreign keys are forbidden on Orbit tables; apply the supported schema before starting")
+	}
 	return nil
 }