I/O and partial inspection

The summary reports transient I/O errors but provides no traceback or filesystem diagnostic. Their cause is not inferred.

Repeated writes to one fixed temporary filename are replaced by:

1. an append-only check journal, flushed and synchronized after each record;

2. unique temporary snapshot files in the destination directory;

3. bounded retries for selected transient I/O errors;

4. independent finalization attempts that do not replace the original numerical exception;

5. an explicit failure status when persistence does not complete.

The temporary-file and replacement facilities are standard Python interfaces PythonIO.

This is not a guarantee against power loss, process termination, disk exhaustion, permissions, or an unavailable filesystem. If persistence fails, inspection is incomplete. Earlier journal records may survive, but are not promoted to a successful inspection.