re: the voice decoder discards up to 87% of a bank — "multi-subwave" refuted

The record table gives a DIRECT binding hokyu_DS_s13A -> VOICE_D_452, where
the corpus records the movie as unbound and movie_manifest_disc.rs asserts
None, citing an in-game verdict that this exact value was "the wrong
recording". That is the only place on the disc where a runtime observation
disagrees with the record table, so it was worth settling.

First, shape: these banks are SHARED. Five slots bind VOICE_D_452, five bind
451, four 450, four 453, three 454 -- 21 hokyu slots over five banks, and the
movies repeat too. Generic resupply cutscenes, not per-stage recordings.

The recorded explanation for 453 decoding to 0.14 s and 454 to 0.43 s was
that the banks are "likely multi-subwave / not cleanly sliced". Refuted: the
count of RIFF magics EQUALS the number of sub-waves recovered in all five
banks, and the last data chunk ends exactly at EOF in four of them. Nothing
between or after sub-waves is being missed.

The real defect: slb::to_xma_riffs finds audio by searching for the RIFF
magic, and a large region PRECEDES it. 87% of VOICE_D_453 and 85% of
VOICE_D_454 sit in front of the first RIFF -- 21-27% zero over 256 distinct
byte values, i.e. content, not padding. VOICE_D_451 is the control: its
leading region is 100% zero, 1 distinct value, real padding.

So the in-game verdict listened to a decode that had discarded most of the
bank, for exactly this bank class. It is evidence about the decoder, not
about the mapping. Note also that what was rejected was a value INFERRED
from a shared demo id; the record table supplies the same value as a stored
field, and only the inference was ever tested.

This does NOT establish the binding is right -- it removes the only recorded
evidence against it. What the leading region actually holds is undecoded, and
confirming the binding needs a human listening.

Artifact: examples/voice_bank_shape.rs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE

docs/re/BACKLOG.md

@@ -1033,6 +1033,24 @@ premise was wrong.**
   Candidates: the **7 `.embsec_` sections** (VAs 0x84D0000–0x86AC000, ~129 KB
   total, executable) or a hashed record in `hidden/MiscBin.pak`. **Finding it
   gives the actual per-phase clear condition for every stage.**
+* ❌ **(2026-08-25) The `.slb` "multi-subwave" guess is REFUTED, and the voice
+  decoder is discarding up to 87 % of a bank.** The record table gives a
+  **direct** binding `hokyu_DS_s13A -> VOICE_D_452` where the corpus records the
+  movie as unbound and a test asserts `None`, citing an in-game verdict that the
+  same value was "the wrong recording". Measured: the RIFF-magic count equals the
+  sub-wave count in all five hokyu banks, so nothing between or after sub-waves
+  is missed — the recorded "likely multi-subwave / not cleanly sliced" is wrong.
+  The audio is lost because a **large region precedes the first RIFF** and
+  `slb::to_xma_riffs` finds audio by searching for that magic: **87 % of
+  `VOICE_D_453` and 85 % of `VOICE_D_454`** sit in front of it, 21–27 % zero over
+  256 distinct byte values — content, not padding. `VOICE_D_451` is the control,
+  its leading region being 100 % zero / 1 distinct value. 🟡 So the in-game
+  verdict tested a decode that had thrown away most of the bank and is **not**
+  evidence against the binding — though it does not confirm it either.
+  ▶️ First step: decode the leading region (it is not padding and not a RIFF —
+  directory? seek table? raw stream?). Then a human has to listen; audio
+  judgement cannot be done in this container. See
+  [`voice-bank-leading-region.md`](voice-bank-leading-region.md).
 * ❌ **(2026-08-25) My own boot-nav diagnosis, MEASURED AND WITHDRAWN.** I said
   the run died because `skip_intro.sh` gates the title test at `rmse <= 1500`
   and the run logged 1503/1549, just above the cut. Measured over a clean