feat(h5): standardize sensor-check into the .h5 (schema v2); SFM reads it

Make the sensor self-check a first-class part of the standardized decoded event
so SFM stops decoding it at report time — device-agnostic, per the store's
decoder→standardized-.h5→SFM model.

  * Event gains a `sensor_check` field; both decoders attach the traces where
    they set raw_samples — series-3 in event_file_io.read_blastware_file
    (minimateplus.sensor_check), series-4 in waveform_store's IDF path
    (micromate.sensor_check).  Covers ingest and backfill (both re-decode).
  * event_hdf5 bumps schema_version 1→2 and writes an optional /sensor_check
    group (raw counts, int32, per channel present).  read_event_hdf5 returns
    it; plot_json_from_hdf5 carries it as a top-level key.  Old v1 files still
    read cleanly (no group → None), so nothing breaks before the backfill.
  * gather_report_data reads sensor_check_waveforms from the .h5 and drops the
    report-time series-3 decode — the report no longer reaches into a decoder,
    and a series-4 event now lights up the same strip automatically.

Stored as raw counts (a shape diagnostic, rendered fit-to-box): the per-series
count scale differs and a physical mic unit is ill-defined, so conversion would
add complexity for no display benefit — easy to add later if a numeric use
appears.

Tests: .h5 roundtrip + backward-compat + plot_json + real series-3 decode
attaches to the Event.

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

sfm/waveform_store.py

@@ -662,6 +662,11 @@ class WaveformStore:
             ev.raw_samples = idf_samples
             n_samples = max((len(idf_samples.get(ch, [])) for ch in ("Tran", "Vert", "Long", "MicL")), default=0)
             ev.total_samples = ev.total_samples or n_samples
+            # Sensor self-check traces from the IDFW fixed header (waveform
+            # events only; {} on histograms / when absent).  Carried on the
+            # bridged Event so the .h5 writer persists them like series-3.
+            from micromate.sensor_check import decode_idf_sensor_check
+            ev.sensor_check = decode_idf_sensor_check(idf_bytes) or None
 
         # For IDFH histograms there are no per-sample waveform arrays — the
         # device stores one peak ADC count per interval per channel.  Synthesise