Put sound in the packed container, and find the padding is a rate error

ROADMAP P6b, FINDINGS 67.  DLXP2: a 64-byte header and then groups -- one
audio lump of A sectors, then F records -- so record i is at
off_frm + i*rec + (i//F)*A*512 and lump k at off_aud + k*(F*rec + A*512).
Still no index and still none needed, which is the packed branch's whole
claim surviving the one change that could have ended it.  The player carries
the third term in six instructions once a frame and zero parsing, and 120 of
120 records are still pixel-exact off a real MB89352 volume with the
interleave in, against a silent control that says no picture byte moved.

The finding is what 65.3 called padding.  A lump is 7,168 B of SPACE; eleven
frames of audio is 7,161.4583... B, so the payload alternates 7,161 and
7,162 and the rest is zero.  A player that fed the chip the whole lump --
which is what "14 sectors every 11 frames" invites -- runs 0.09% fast, and
that is not waste, it is drift: 0.84 ms a group, 1.25 s of lip-sync over the
game's 22.8 minutes.  What a player carries is one accumulator,
acc += 11*15625; n = acc//24; acc %= 24, which is clock.i's shape for
clock.i's reason and the third time this tree has met the pattern.

The four ADPCM axes ride in the header as fields rather than a version
number, and the gate flips each one to prove they earn it: nibble order
-31.99 dB, delta formula -24.86, clamp 0.00, accumulator -0.49.  Nothing
parses a packed container, so the gate partitions the whole file -- 131
spans, no overlap, no gap -- and asserts what a cadence-blind player would
read: exactly records 11..119 wrong, and frames 0..10 identical either way,
which is how an off-by-one like that survives a rig that checks frame 0.

Wire 582.0 + 7.64 = 589.6 KB/s, 65.3's prediction to the tenth.

Green light ALL GREEN before (tmp/check_s35_start.log) and after
(tmp/check_s35_end.log), with the new stage in it.

Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6

docs/ROADMAP.md

@@ -115,6 +115,24 @@ loudest passage on the disc is unmeasured. **(2) The transport is P6b's, not
 scaffolding**, and it worked first time. **P6b is next and its bytes are
 decided: DLXP2 encodes with `adpcm.CHIP`.**
 
+Amended end of session 35: **P6b IS DONE AND ITS PADDING WAS DRIFT (FINDINGS
+67).** DLXP2 exists: a 64-byte header, groups of one `A`-sector audio lump then
+`F` records, `record i = off_frm + i*rec + (i//F)*A*512` — **still no index and
+still none needed**, which is the packed branch's whole claim surviving the one
+change that could have ended it. The player carries it in **six instructions
+once a frame**, and 120 of 120 records are still pixel-exact off a real volume
+with the interleave in, against a **silent control** that says no picture byte
+moved. **65.3's 0.09% was not waste, it was a rate error**: a lump is 7,168 B of
+space and eleven frames of audio is 7,161.4583… B, so a player that fed the chip
+the whole lump would run 0.09% fast — **1.25 s of lip-sync over the game's 22.8
+minutes**. The payload is a remainder, `acc += 11*15625; n = acc//24; acc %= 24`,
+which is `clock.i`'s shape for `clock.i`'s reason and the **third** time this
+tree has met the pattern. The four ADPCM axes ride in the header and the gate
+flips each one to prove they earn it (**order −31.99 dB, formula −24.86**). The
+wire is **589.6 KB/s**, 65.3's figure to the tenth. **What is left of P6 is the
+last quarter: no audio has been played out of this container on any layer, and
+two DMA channels have never run at once.**
+
 **THE COMPLETION TARGET IS M3, THE VERTICAL SLICE** (USER DECISION): one scene
 tree — a decision point, two outcomes, a death clip — with audio, streaming from
 a real SCSI volume on a stock 2 MB machine, playable. That is the point at which
@@ -747,10 +765,28 @@ throughout (65.5). The gap is the register semantics, and the way to close it is
 machine that is known-correct because Sharp wrote it. That is also the real
 design, so it is not scaffolding.
 
-**P6b. A CONTAINER WITH SOUND IN IT.** DLXP1 has no audio section. 65.3 is the
-arithmetic a DLXP2 is built from and no byte of one is written. It waits on P6a,
-because a container full of audio encoded against the wrong formula is 25 dB of
-work to redo.
+**P6b. A CONTAINER WITH SOUND IN IT. DONE, session 35 — FINDINGS 67.**
+~~DLXP1 has no audio section. 65.3 is the arithmetic a DLXP2 is built from and no
+byte of one is written.~~ DLXP2 is written, gated and carried by the player:
+`tools/encoder/dlxp.py`, `pack.py --audio`, `tools/analysis/34_packed_audio.py`,
+the third LBA term in `src/player/packed.s`. The cadence arithmetic came through
+unchanged (F=11, A=14, 589.6 KB/s) and the **payload** did not: a lump's audio is
+7,161 or 7,162 B of a 7,168 B sector run, and feeding the chip the whole lump
+drifts 1.25 s over the game.
+
+**P6c. AUDIO OUT OF THE CONTAINER, ON THE MACHINE (new, session 35).** Every
+piece exists and none is joined up. The container carries the bytes (67); the
+transport is `src/player/adpcm.i`'s channel-3 configuration, which is the IPL
+ROM's own and worked first time (66.1). What is missing is **the lump buffer**
+— 14,336 B, double-buffered, allocated by nobody — and **the remainder
+accumulator**, which is three instructions and is not optional.
+
+**And the interaction neither half has met: TWO CHANNELS AT ONCE.** The video
+channel holds the bus and halts the 68000, which already costs the frame clock
+half its ticks without the clock being able to tell (64.3). An audio channel
+that must be serviced *during* that hold has never been run. 52's 1.25%..1.48%
+of a frame is a figure measured in isolation, and `32_audio_wire.py` names what
+it turns into here: audio does not merely cost clocks, it costs **darkness**.
 
 **E6. Container v2** — audio interleave, per-record index, scene table. Depends
 on P6's answer and on P5's index.
@@ -878,10 +914,12 @@ B2 blanking ─┬─ NOT blanked ─> K3's DMAC-DIRECT player is the one: 54.9%
                                 picks a different player.
 B1 BURST rate (NEW, 64.2) ──> which of the two K3/K4 wins, if B2 blanks
 
-P6 audio DONE bar one (65): encoder gated, cadence F=11/A=14, 589.6 KB/s
-  └─> P6a WHICH DELTA FORMULA? ─┬─ needs no board: MAME has :okim6258
-      worth 25 dB, so it is a   │  at $E92001/$E92003 (65.5)
-      PRECONDITION not a tweak  └─> then P6b, a container with sound in it
+P6 audio: encoder gated (65), P6a the chip's own decoder measured (66),
+  P6b DLXP2 written and gated, 589.6 KB/s on the wire (67)
+  └─> P6c AUDIO OUT OF THE CONTAINER ─┬─ the bytes exist, the transport
+      needs no board: the transport   │  exists, the lump buffer does not
+      is the IPL ROM's own (66.1)     └─> TWO CHANNELS AT ONCE, which is
+                                         the one thing nothing has run
 ```
 
 **Read that top-left branch as the project's live question.** Everything else