fix: add STRT invalid detction, ach server passes config for get events,

CLAUDE.md

@@ -191,6 +191,18 @@ rectime_seconds = int(round((total_samples - pretrig_samples) / sample_rate))
 `_decode_a5_waveform` uses `sample_rate=1024` as a default; the server overrides with
 `compliance_config.sample_rate` when available.  Do NOT use `strt[18]` for rectime.
 
+**Pre-trigger time is separate from record_time (confirmed 2026-04-14):**
+Blastware documentation states: "The default Time Scale is -0.25 second to 1 second — this
+negative number accounts for the pre-trigger set for compliance monitoring."  Therefore:
+- `record_time` (3.0 s) is POST-TRIGGER duration only
+- Pre-trigger = 0.25 s = 256 samples at 1024 sps (compliance monitoring standard default)
+- The pre-trigger field has NOT yet been located in the raw compliance config bytes
+- When STRT layout is invalid, `_decode_a5_waveform` falls back to pretrig = 0.25 × sr
+- TODO: locate pretrig_time offset in ComplianceConfig — search around anchor or channel blocks
+
+The device bulk-streams zero-padded frames BEYOND the configured record window.  The
+viewer clips `displayCount = total_samples = pretrig + post_trig` to exclude this padding.
+
 **Sanity check — pretrig_samples must be less than total_samples:**
 If `pretrig_samples >= total_samples` the STRT parse is invalid.  Possible causes:
 DLE-stuffed `0x10` byte within prev_key4 or key4 shifted field offsets, or a different