codec-re: add Waveform body codec section to CLAUDE.md

Mirrors the structural findings now documented in
docs/instantel_protocol_reference.md §7.6.1: block framing solved,
Tran segment-0 decode verified across 5 fixture events, multi-segment
continuation still open. Also adds waveform_codec.py to the project
layout map.

CLAUDE.md

@@ -17,6 +17,8 @@ minimateplus/         ← Python client library (primary focus)
   protocol.py         ←   MiniMateProtocol — wire-level read/write methods
   client.py           ←   MiniMateClient — high-level API (connect, get_events, …)
   models.py           ←   DeviceInfo, EventRecord, ComplianceConfig, …
+  waveform_codec.py   ←   Body-codec block walker + decode_tran_initial (partial
+                          per-sample decoder — see "Waveform body codec" section below)
 
 sfm/server.py         ← FastAPI REST server exposing device data over HTTP
 seismo_lab.py         ← Tkinter GUI (Bridge + Analyzer + Console tabs)
@@ -57,6 +59,61 @@ Full read pipeline + write pipeline + erase pipeline + monitor log + call home c
 
 ---
 
+## Waveform body codec — PARTIAL (2026-05-11)
+
+The **per-byte decoding** of the Blastware waveform-file body (between the
+21-byte STRT record and the 26-byte footer) was historically claimed to be
+"raw int16 LE, 8 bytes per sample-set."  That was wrong — see the
+retraction in `docs/instantel_protocol_reference.md §7.6.1`.  The body
+is actually a tagged-block stream with a custom delta+RLE codec.
+
+### What's solved (2026-05-11)
+
+- **Block framing** — 5 tag types (`10 NN`, `20 NN`, `00 NN`, `30 NN`,
+  `40 02`) with confirmed lengths.  Implementation: `walk_body()` in
+  `minimateplus/waveform_codec.py`.
+- **Tran channel segment 0** — preamble bytes [3:7] = `Tran[0]`, `Tran[1]`
+  as int16 BE in **16-count units** (LSB = 0.005 in/s).  Then `10 NN`
+  (4-bit nibble deltas), `20 NN` (int8 deltas), and `00 NN` (RLE zero
+  deltas) carry Tran deltas from sample 2 onward.  Verified byte-perfect
+  across 4 of 5 fixture events (510 samples each).  Implementation:
+  `decode_tran_initial()`.
+- **Segment header** — `40 02` is a 20-byte block.  Payload bytes [0:2]
+  are the T_delta at the start of the new segment (int16 BE).  Bytes
+  [6:8] are the byte length to the next segment header.  Bytes [8:12]
+  are a monotonic uint32 LE counter.  Bytes [12:14] are constant `02 00`.
+
+### What's NOT solved
+
+- **Tran past segment 0** — multi-segment Tran continuation has been
+  attempted but every hypothesis tested breaks at sample ~512.  Likely
+  channels rotate across segments (e.g. segment 0 = Tran, segment 1 = Vert,
+  …) but this is unverified.
+- **Vert / Long / Mic channels** — no per-channel decoder yet.  These
+  almost certainly live in later segments but the segment-to-channel
+  mapping is open.
+- **The `30 NN` block content** — appears in loud-from-start events
+  (SS0, SV0) and breaks the simple Tran walk there.  Probably a channel-
+  switch or alternative-encoding marker for high-amplitude regions.
+
+### Production-code status
+
+`client.py:_decode_a5_waveform` still uses the old (broken) int16 LE
+decoder.  Until the multi-channel decoder lands, the `.h5` sidecars
+produced by SFM contain WRONG samples — keep treating them as
+"unverified" downstream.  `decode_waveform_v2()` returns `None` as a
+placeholder.
+
+### Test fixtures
+
+`tests/fixtures/decode-re-5-8-26/` and `tests/fixtures/5-11-26/` —
+seven BW binary + ASCII pairs captured from a live BE11529.  The
+5-11-26 high-amplitude bundle (PPV 6–7 in/s) is what cracked the Tran
+codec; the V70 (mic-heavy) + JQ0 (Vert-heavy) pair cracked the `00 NN`
+RLE rule.
+
+---
+
 ## Protocol fundamentals
 
 ### DLE framing