feat(backfill): regenerate .h5 with /sensor_check; TOOL_VERSION 0.31.0

Complete the sensor-check standardization: existing events need their .h5
regenerated to gain the v2 /sensor_check group.

  * backfill_thor_events.py attaches the decoded series-4 traces
    (micromate.sensor_check) on its own IDF decode path, mirroring
    save_imported_idf, so regenerated Thor .h5 files get the group. Series-3
    backfill needs no change — it re-decodes via read_blastware_file, which now
    attaches the traces itself.
  * TOOL_VERSION 0.30.0 → 0.31.0 so the standard backfill regenerates every
    event (no --force): the tool now produces the /sensor_check group. Purely
    additive — no decoded value changes.
  * CHANGELOG (Unreleased): sensor-check now series-3 + series-4, standardized
    into the .h5 (schema v2), with the ⚠ backfill note; FFT + compliance stay
    no-backfill (they read existing .h5 samples).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDXjZCr4RqT2U3QvMDhgzf

scripts/backfill_thor_events.py

@@ -305,6 +305,11 @@ def main(argv=None) -> int:
                                 default=0,
                             )
                             ev.total_samples = ev.total_samples or n_samp
+                            # Sensor self-check traces from the IDFW fixed
+                            # header, so regenerated .h5 files gain the v2
+                            # /sensor_check group (mirrors save_imported_idf).
+                            from micromate.sensor_check import decode_idf_sensor_check
+                            ev.sensor_check = decode_idf_sensor_check(binary_bytes) or None
 
                         event_hdf5.write_event_hdf5(
                             hdf5_path, ev,