feat(audio): Phase E.2 OpenAL engine + SoundTable cookbook + hook wiring

Full audio pipeline from MotionHook → OpenAL 3D playback. Faithful to
retail's 16-voice pool, inverse-square falloff, and SoundTable
probabilistic variant selection.

Core layer (AcDream.Core/Audio):
- WaveDecoder parses the WAVEFORMATEX in Wave dat headers. PCM
  (wFormatTag=1) decodes directly; MP3 (0x55) and ADPCM (0x02) return
  null + log (ACM compressed decoders need Windows winmm; cross-platform
  path deferred). Cites r05 §2.1-2.3 + ACE Wave.cs.
- SoundCookbook.Roll implements the probability-weighted entry pick that
  gives retail footsteps their variation. Cumulative-distribution walk;
  silence tail when probabilities sum to <1.
- DatSoundCache: ConcurrentDictionary-backed lazy load of Wave /
  SoundTable dats, decoded PCM memoized.

App layer (AcDream.App/Audio):
- OpenAlAudioEngine (Silk.NET.OpenAL): 16-source 3D pool with
  round-robin first-free, then evict-quieter-slot algorithm matching
  retail chunk_00550000.c FUN_00550ad0 exactly. Separate 4-source UI
  pool (source-relative). AL buffer cache keyed by Wave id.
  InverseDistanceClamped distance model. Fail-open when AL driver
  missing or ACDREAM_NO_AUDIO=1 — client continues without audio.
- AudioHookSink routes SoundHook / SoundTableHook / SoundTweakedHook
  from the Phase E.1 animation-hook router into OpenAL. All three
  hook types fire on both player AND NPCs/monsters (the sequencer
  dispatches per-entity and the sink uses entity worldPos for 3D pan).
- DictionaryEntitySoundTable holds per-entity SoundTable mapping,
  populated from Setup.DefaultSoundTable at hydration time. Server-
  sent overrides would take precedence here when wired.

GameWindow integration:
- OpenAL init in OnLoad after dat collection, suppressible via
  ACDREAM_NO_AUDIO=1.
- SetListener called each OnRender frame with camera position + view
  basis vectors (fwd = -Z, up = +Y of inverse view).
- AudioEngine disposed in OnClosing before dats.

Tests: 6 WaveDecoder (PCM / MP3-null / ADPCM-null / stereo / truncated
/ peek) + 6 SoundCookbook (empty / single / 50-30-20 distribution
within 5%, silence tail, table lookup, missing table key). Verified
against r05 §2 + ACViewer export-path.

Build green, 497 tests pass (up from 485).

Ref: r05 §2 (Wave format), §5.3 (16-voice pool + eviction).
Ref: FUN_00550ad0 (chunk_00550000.c:527) eviction algorithm.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/AcDream.App.csproj

@@ -13,6 +13,9 @@
     <PackageReference Include="Silk.NET.OpenGL" Version="2.23.0" />
     <PackageReference Include="Silk.NET.Windowing" Version="2.23.0" />
     <PackageReference Include="Silk.NET.Input" Version="2.23.0" />
+    <PackageReference Include="Silk.NET.OpenAL" Version="2.23.0" />
+    <PackageReference Include="Silk.NET.OpenAL.Extensions.Creative" Version="2.23.0" />
+    <PackageReference Include="Silk.NET.OpenAL.Extensions.EXT" Version="2.23.0" />
     <PackageReference Include="Serilog" Version="4.0.2" />
     <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
     <PackageReference Include="StbTrueTypeSharp" Version="1.26.12" />