Detect SQLITE database locked

### What would you like help with?

Hi,

Is there an explicit error code that would allow me to detect when a SQLITE update/insert fails because the database is locked? Currently I'm checking if the `message` field from `AdbcError` ends with `database is locked`, but that feels brittle.

Thanks.

Start by tracing how SQLite reports a locked database and how that failure is exposed through AdbcError; the issue names no source files or tests. The work is complete when callers can reliably identify the locked-database condition without matching the message text, with coverage for the resulting error behavior.

Written by the indexing model from the issue text.