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

minimateplus/models.py

@@ -544,6 +544,15 @@ class Event:
     pretrig_samples: Optional[int] = None   # from STRT record: pre-trigger sample count
     rectime_seconds: Optional[int] = None   # from STRT record: record duration (seconds)
 
+    # Sensor self-check traces keyed by channel label — the short diagnostic
+    # waveforms the unit records when it pulses each sensor before monitoring
+    # (geophone ring-downs + a mic pulse train).  Decoded from the binary by
+    # the per-series decoder (minimateplus.sensor_check / micromate.sensor_check)
+    # and carried here so the .h5 writer can persist them device-agnostically.
+    # Raw ADC counts; the source series' scale differs but the trace is a
+    # shape diagnostic (rendered fit-to-box).  None when absent.
+    sensor_check: Optional[dict] = None     # {"Tran": [...], ..., "MicL": [...]}
+
     # ── Debug / introspection ─────────────────────────────────────────────────
     # Raw 210-byte waveform record bytes, set when debug mode is active.
     # Exposed by the SFM server via ?debug=true so field layouts can be verified.