Same as process_command_with_render but takes a pre-parsed
Statement. SQLR-23 — Statement / Connection::prepare_cached
dispatch through this entry point so they pay the sqlparser cost
once at prepare time, not per execute.
Backwards-compatible wrapper around process_command_with_render that
returns just the status string. Every existing call site (the public
Connection::execute, the SDK FFI shims, the .ask meta-command’s
inline runner, the engine’s own tests) keeps working unchanged.