codec-re: 00 NN is RLE; full Tran segment-0 decode (4 of 5 events)

User uploaded a Vert-heavy event (JQ0) and a Mic-heavy event (V70).
Those two were exactly what was needed to crack the next piece:

- 00 NN block = run-length-encoded zero deltas in the current channel.
  Append NN copies of the current cumulative value (no change).
- find_data_start now recognizes 00 NN as a valid first tag (some events
  begin with a leading 00 NN RLE block).
- decode_tran_initial now decodes the FULL segment 0 (not just the first
  data block).

Results across 5 fixture events:
  - M529LL1A.SP0 (loud-all-channels)  : 510 / 510  ✓
  - M529LL1L.JQ0 (Vert-heavy)         : 510 / 510  ✓
  - M529LL1L.V70 (Mic-heavy)          : 510 / 510  ✓
  - M529LL1A.SV0 (loud-from-start)    :  58 /  58  ✓
  - M529LL1A.SS0 (loud-from-start)    :  42 / 502  (stops at first 30 04)

The 30 04 block (only seen in loud-from-start events) hasn't been
decoded yet — likely a channel-switch marker for the high-amplitude
regime.

Also discovered: segment header (40 02) payload bytes [0:2] = T_delta
at first sample of new segment, [6:8] = byte length to next segment.
Multi-segment Tran decoding still diverges after sample 512 because
the per-segment channel ordering after the header is unknown.

Tests: 40 pass (up from 36).

Files:
- minimateplus/waveform_codec.py: find_data_start fix, RLE handling,
  full segment-0 decode in decode_tran_initial
- tests/test_waveform_codec.py: synthetic RLE test, full segment 0
  tests for JQ0 and V70
- tests/fixtures/5-11-26/: M529LL1L.JQ0, M529LL1L.V70 + TXT exports
- docs/instantel_protocol_reference.md §7.6.1: RLE + segment-header docs

analysis/multi_segment.py

@@ -0,0 +1,81 @@
+"""Decode Tran across multiple segments by resetting at 40 02 headers."""
+import sys
+sys.path.insert(0, ".")
+from analysis.load_bundle import _parse_txt
+from minimateplus.waveform_codec import walk_body, find_data_start
+
+
+def s4(n):
+    return n if n < 8 else n - 16
+
+
+def i8(b):
+    return b if b < 128 else b - 256
+
+
+def decode_full_tran(body):
+    """Decode all Tran samples in the body, walking through segments."""
+    if len(body) < 7 or body[0:3] != b"\x00\x02\x00":
+        return None
+    T0 = int.from_bytes(body[3:5], "big", signed=True)
+    T1 = int.from_bytes(body[5:7], "big", signed=True)
+
+    # Locate first tag
+    i = 7
+    while i + 1 < len(body) and body[i] not in (0x00, 0x10, 0x20, 0x30, 0x40):
+        i += 1
+
+    blocks = walk_body(body, i)
+    T = [T0, T1]
+    cur = T1
+    for bi, blk in enumerate(blocks):
+        if blk.tag_hi == 0x40:
+            # Segment header — try interpreting bytes [0:2] as new T anchor
+            if len(blk.data) >= 2:
+                new_anchor = int.from_bytes(blk.data[0:2], "big", signed=True)
+                # The next sample IS this anchor value, NOT a delta from cur.
+                T.append(new_anchor)
+                cur = new_anchor
+        elif blk.tag_hi == 0x10:
+            for byte in blk.data:
+                for nib in ((byte >> 4) & 0xF, byte & 0xF):
+                    cur += s4(nib)
+                    T.append(cur)
+        elif blk.tag_hi == 0x20:
+            for byte in blk.data:
+                cur += i8(byte)
+                T.append(cur)
+        elif blk.tag_hi == 0x00:
+            # RLE: append NN zero deltas
+            for _ in range(blk.tag_lo):
+                T.append(cur)
+        # 30 NN: skip
+    return T
+
+
+def main():
+    for stem in ("M529LL1L.V70", "M529LL1L.JQ0", "M529LL1A.SP0", "M529LL1A.SS0", "M529LL1A.SV0"):
+        path = f"decode-re/5-11-26/{stem}"
+        with open(path, "rb") as f:
+            body = f.read()[43:-26]
+        _, samples = _parse_txt(path + ".TXT")
+        truth_T = [round(v*200) for v in samples["Tran"]]
+        n_truth = len(truth_T)
+
+        decoded = decode_full_tran(body)
+        n = min(len(decoded), n_truth)
+        matches = sum(1 for i in range(n) if decoded[i] == truth_T[i])
+        # Find first divergence
+        div_at = -1
+        for i in range(n):
+            if decoded[i] != truth_T[i]:
+                div_at = i
+                break
+        print(f"{stem}: decoded={len(decoded)}, truth={n_truth}, matches={matches}/{n}, first div={div_at}")
+        if div_at >= 0 and div_at < 30:
+            print(f"  truth around div [{max(0,div_at-3)}:{div_at+8}]: {truth_T[max(0,div_at-3):div_at+8]}")
+            print(f"  pred  around div [{max(0,div_at-3)}:{div_at+8}]: {decoded[max(0,div_at-3):div_at+8]}")
+
+
+if __name__ == "__main__":
+    main()