ParseAlarms took the 76-byte vendor layout whenever Length % 76 == 0, so a legacy 80-byte
reply of exactly 19 records (1,520 B = 20 x 76) decoded as 20 garbage vendor records.
The response block carries no record count (its 16-byte header is length/class/path/
command/rc/payload length), so the layout is chosen from what is known: the record count
the request asked for (a reply never holds more), then each layout's field invariants on
every record. For legacy records, the int32 type/axis/length must fit a short and the
length must be at most 64. For vendor records, the i16 length must be at most 64. If both
still fit, the layout whose declared lengths match the decoded text wins. Vendor stays the
default when both readings are equally plausible, and unambiguous lengths are unchanged.
Refs #740
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
29b566d51b