P1: closing a JDBC connection after unconfirmed rollback can commit pending writes #237

Follow-up to review-only draft #236 at edbae2b. JdbcSqlExecutor.executeInTransaction skips setAutoCommit restoration after rollback cannot be confirmed, but its outer finally still calls connection.close(). The Java SE Connection contract says close with an active transaction has implementation-defined results: https://docs.oracle.com/en/java/javase/17/docs/api/java.sql/java/sql/Connection.html . A DataSource/pool wrapper may commit during close or reset, so this cleanup is not generically rollback-safe.\n\nProposed deterministic counterexample: a SQLite-backed Connection proxy fails rollback while keeping the transaction open; its close emulates a valid commit-on-close policy. The executor must report TRANSACTION_OUTCOME_UNKNOWN and must not call that unsafe close path. Consider abort/invalidate as the default fail-closed disposal path, with a clear operational warning if abort itself fails. Preserve the original uncertain outcome and ledger reload guard. This issue is a review finding, not a claim that every JDBC driver commits on close.