`_export_timings` parsed message timestamps with a bare `float()`, so a
pre-existing out-of-range cell (e.g. 8.4e252) reached
`datetime.fromtimestamp` and raised OverflowError, killing the whole
`export_session`/`export_all` call — a regression caught by
tests/hermes_state/test_corrupt_row_robustness.py. Route the cell through
`coerce_epoch`, the reader every other timestamp surface already uses, so a
bad row degrades to a `missing` count (with the usual warning naming the
session) and the export still lands.
teknium1
2a92d6be4d