feat: update event iteration logic to use null sentinel for end-of-events detection

CLAUDE.md

@@ -2,7 +2,7 @@
 
 Ground-up Python replacement for **Blastware**, Instantel's Windows-only software for
 managing MiniMate Plus seismographs. Connects over direct RS-232 or cellular modem
-(Sierra Wireless RV50 / RV55). Current version: **v0.6.0**.
+(Sierra Wireless RV50 / RV55). Current version: **v0.7.0**.
 
 ---
 
@@ -135,6 +135,26 @@ the setup at record time, not the current device config — this is why we fetch
 `stop_after_metadata=True` (default) stops the 5A loop as soon as `b"Project:"` appears,
 then sends the termination frame.
 
+### SUB 1E / 1F — event iteration null sentinel (FIXED, do not re-introduce)
+
+**The null sentinel for end-of-events is `event_data8[4:8] == b"\x00\x00\x00\x00"`, NOT
+`key4 == b"\x00\x00\x00\x00"`.**
+
+Event 0's waveform key is `00000000` — all-zero key4 is a valid event address.
+Checking `key4 == b"\x00\x00\x00\x00"` exits the loop immediately after the 1E call,
+seeing event 0's key and incorrectly treating it as "no events."
+
+Confirmed from the 4-3-26 two-event capture (`bridges/captures/4-3-26-multi_event/`):
+
+```
+1E response (event 0):  key4=00000000  data8=0000000000011100  ← valid, trailing bytes non-zero
+1F response (event 1):  key4=0000fe00  data8=0000fe0000011100  ← valid
+1F null sentinel:       key4=0000fe00  data8=0000fe0000000000  ← done, trailing 4 bytes = 00
+```
+
+`advance_event()` returns `(key4, event_data8)`.
+Callers (`count_events`, `get_events`) loop while `data8[4:8] != b"\x00\x00\x00\x00"`.
+
 ### SUB 1A — compliance config — orphaned send bug (FIXED, do not re-introduce)
 
 `read_compliance_config()` sends a 4-frame sequence (A, B, C, D) where: