chore(audio): Campaign A slice A6 — delete what retail does not have

Retail EoR has no music system: the linked winmm MIDI player has zero
callers, 'music' appears zero times in the 65 MB decomp, SoundType has no
music member, InitPrefs registers no music key, and the install ships no
music files. So PlayMusic/StopMusic/MusicVolume and the AudioSettings
Music knob are deleted rather than left as an API modelling dead code —
the string-keyed signature was the tell, since every other entry point is
DID-keyed. Old settings.json files carrying a 'music' key still load; the
reader ignores unknown keys and the next save drops it.

The Ambient slider is now surfaced, because slice A5 gave it something to
drive, and its default returns to retail's 1.0 from an invented 0.8 —
InitPrefs defaults every sound preference to unity. The panel rule is
unchanged: no slider that does nothing.

r05-audio-sound.md gets a SUPERSEDED banner naming its five wrong
sections (falloff, pan, voice pool, selection, music, ambient) so a
future reader reaches the lane notes instead of the Ghidra-era reads that
this campaign spent its first two slices undoing.

TS-9 re-scoped from 'any MP3 cue' to the measured blast radius: exactly 1
MP3 among 786 shipped waves, a ~2 s mono clip. Its original framing
assumed a music system that does not exist. The ADPCM count remains
unmeasured and is named as the open question.

Deferred deliberately: #321's sound-cache decode-dedup race. It is a
pre-existing concurrency flake rather than audio-parity behaviour, and
shipping a speculative fix to a race I have not reproduced is exactly the
shortcut this project's no-workarounds rule exists to prevent.

Campaign A is code-complete; the plan carries the closeout.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/architecture/retail-divergence-register.md

@@ -341,7 +341,7 @@ AP-94..AP-112 for the confirmed retail-UI completion gaps.
 | TS-6 | Weather particle emission suppressed — all weathery DayGroups map to Overcast (correct fog/cloud tone, no precipitation); retail's camera-attached weather subsystem not yet located in the decomp | `src/AcDream.Core/World/WeatherState.cs:200` | Decomp research verified the sky loop never reads `DefaultPesObjectId`; an earlier name-based rain spawn regressed (rained where retail didn't, 2026-04-23) — inventing a name→rain path is forbidden until the real subsystem is found | Rainy/snowy/stormy days never show retail's precipitation effects (permanent missing visuals until the subsystem is found and ported) | FUN_00508010 / FUN_0051bed0→FUN_0051bfb0 (negative findings) |
 | TS-7 | SkyObject `weather_enabled` gate not honored — weather-flagged sky objects (bit 0x04) always instantiate | `src/AcDream.Core/World/SkyDescLoader.cs:50` | No weather_enabled toggle exists yet; IsWeather flag parsed + documented as the gate to wire | Weather-only sky meshes (rain cylinders) appear where retail-with-weather-off suppresses them | `GameSky::MakeObject` 0x00506ee0, guard at decomp:268630 |
 | ~~TS-8~~ | **RETIRED 2026-07-31 (#268 stat-chain closeout).** `EnchantmentWireReader` parses the complete 0x02C2 payload and `GameEventWiring` publishes its StatMod type/key/value and bucket through the same `ActiveEnchantmentRecord` used at login. An end-to-end dispatch test proves a mid-session skill modifier changes `LocalPlayerState.GetEffectiveSkill` immediately. | `src/AcDream.Core.Net/Messages/EnchantmentWireReader.cs`; `src/AcDream.Core.Net/GameEventWiring.cs`; `tests/AcDream.Core.Net.Tests/GameEventWiringTests.cs` | — | — | `CEnchantmentRegistry::EnchantAttribute @ 0x00594570`; `CEnchantmentRegistry::EnchantSkill @ 0x005947B0`; holtburger `messages/magic/types.rs` |
-| TS-9 | MP3 (0x55) and MS-ADPCM (0x02) waves undecoded — affected sounds skipped; retail decoded both via winmm ACM | `src/AcDream.Core/Audio/WaveDecoder.cs:33` | Managed decoder (NAudio or similar) deferred; PCM covers the vast majority of ~3500 waves | Any MP3 (common for music-ish clips) or ADPCM cue plays as silence where retail plays it | winmm ACM path (r05 §2.1) |
+| TS-9 | **RE-SCOPED 2026-08-08 (Campaign A slice A6) — the blast radius is one wave, measured.** MP3 (0x55) and MS-ADPCM (0x02) waves still decode to null and play as silence where retail decoded both through the winmm ACM. What changed is the size of the problem: an independent walk of the shipped dats found exactly **1 MP3 among 786 waves** (`0x0A000393`, a ~2 s mono clip) and the row's original "any MP3 cue, common for music-ish clips" framing was wrong — it was written when we believed retail had a music system, and retail has none. A managed decoder for one two-second asset is not worth the dependency; the honest options are a ~50-line decode or an accepted-loss row, and this row is now the accepted-loss record. The ADPCM count has NOT been measured and is the one open question here. | `src/AcDream.Core/Audio/WaveDecoder.cs:33` | Measured rather than assumed. PCM covers 785 of 786 waves. | One ~2 s clip is silent, plus an unmeasured number of ADPCM clips. | winmm ACM path; dat census in `docs/research/2026-08-08-audio-retail-dat-layer.md` §4c |
 | TS-14 | Setup `Flatten` ignores ParentIndex part hierarchy (treats every placement as root-local); still in production use (GameWindow hydration, SkyRenderer) | `src/AcDream.Core/Meshing/SetupMesh.cs:15` | Most Setups are flat single-level rigs where root-local equals composed; hierarchical composition deferred ("Phase 3") | Any Setup with genuinely nested parts renders them at wrong offsets — mis-assembled multi-part objects in the Flatten paths | retail Setup ParentIndex chain composition |
 | TS-15 | No distance-driven degrade (LOD): always close-detail slot 0; plus the **#47** static `Degrades[0]` swap for 34-part humanoids only (structural sentinel detector) | `src/AcDream.Core/Meshing/GfxObjDegradeResolver.cs:57` (+ `src/AcDream.App/Rendering/GameWindow.cs:2608`) | LOD plumbing doesn't exist; slot 0 is correct for player + nearby NPCs; #47 closed the visible low-detail-arms bug without porting UpdateViewerDistance | Distant objects render max-detail (perf + wrong visuals where far meshes intentionally differ/hide parts); a future 34-part non-humanoid matching the sentinel gets the wrong mesh swap | `CPhysicsPart::UpdateViewerDistance` 0x0050E030; ::Draw 0x0050D7A0; ::LoadGfxObjArray 0x0050DCF0 |
 | TS-17 | AttackConditions suffix always empty in combat chat — formatting ported, wire bitflag not plumbed (Phase I.7 follow-up) | `src/AcDream.Core/Chat/CombatChatTranslator.cs:233` | Only the wire plumbing is missing; the holtburger-ported formatter is ready | Combat log omits "[Sneak Attack]"-style suffixes retail displays — hidden combat-mechanic feedback | holtburger chat.rs:588-595 |