[TBL] nGEM eto reaches 268 ms in CODA data; default 0–71 ms TOA range would drop ~73% of events #1353

In the two most recent TBL CODA files, nGEM event_time_offset (eto) spans 0–268.4 ms (just below 2²⁸ ns). The TBL nGEM view (ngem_detector_view, TOA-only) uses the default TOA edges of 0–71.43 ms (parameter_models.py:26). If the real detector delivers data like this, the view and its NICOS devices (ngem_detector_counts_total, ngem_detector_image) see only about 27% of the events. counts_total is the sum of the TOA histogram (#1242), so the NICOS reading would be low without any visible sign.

The CODA data may not be real detector data. nGEM may be fed by a simulator. Several features point that way:

• every message carries exactly 4 events
• event_time_zero comes at 10 Hz on its own grid, not the 14 Hz timing system
• eto is flat over the whole 0–268 ms range

Neither run had beam.

To do

• Find out from the detector group / ECDC what eto range the real nGEM readout delivers, and whether it is referenced to the 14 Hz ESS pulse.
• If the real range exceeds 71.43 ms, give the nGEM view an instrument-specific default for the TOA edges. Until then, operators can set the upper edge to ≥ 268.4 ms in the dashboard.
• If eto is not referenced to the ESS pulse, TOA has no physical meaning for nGEM. The view should then probably not histogram by TOA at all.

Found while investigating #1352.