Split audio host contract

docs/PROJECT-STRUCTURE.md

@@ -163,8 +163,9 @@ of that state through the sealed partial class.
 `engine/Age.Engine/Hosting/IHost.cs` remains the aggregate runtime host accepted by the VM and existing host
 implementations. `engine/Age.Engine/Hosting/IDiagnosticHost.cs` owns recoverable-warning and modal-diagnostic
 reporting contracts, while `engine/Age.Engine/Hosting/ILifecycleHost.cs` owns script-context entry/exit, sleep and
-timed-deadline waiting, frame yield, and scene reset. `IHost` inherits both focused contracts; their required and
-default behavior is unchanged.
+timed-deadline waiting, frame yield, and scene reset. `engine/Age.Engine/Hosting/IAudioHost.cs` owns BGM, voice,
+SFX, fade, volume, and route-control contracts, including the compatibility overload/default chains used by
+simple hosts. `IHost` inherits all three focused contracts; their required and default behavior is unchanged.
 
 `engine/Age.Engine/Model/GfxState.cs` retains cross-domain retained-graphics coordination.
 `engine/Age.Engine/Model/GfxState.Contracts.cs` owns its public render, transition, diagnostic, persistence,

docs/remake-architecture-and-roadmap.md

@@ -765,6 +765,11 @@ do not mix mechanical moves with semantic changes.
    entry point; all required members, default implementations, existing hosts, and transport-record locations
    are unchanged. Runtime validation remains green.
 
+   The second bounded contract slice introduced `IAudioHost` for BGM, voice, sound-effect, fade, volume, and
+   route-control operations. `IHost` inherits the focused contract; all fifteen members, required implementations,
+   compatibility overloads/default chains, and existing host classes remain behaviorally unchanged. Runtime
+   validation remains green.
+
 4. **Make the build graph express source ownership.** Stop linking production `.cs` files from `godot/` and
    `tools/movie-corpus-gate/` into `Age.Engine.Tests`. Extract the platform-neutral frontend/movie/diagnostic
    code into a small production project referenced by Godot, tests, and the corpus gate. Retain both existing
@@ -1124,9 +1129,9 @@ layer's rendering diverges from ADV; save layout.
 
 ## 8. Immediate next step
 Continue step 3 of the **codebase consolidation** maintenance slice: clarify runtime contracts without changing
-behavior or the aggregate host accepted by the VM. With diagnostic and lifecycle contracts established beneath
-`IHost`, introduce the audio host contract next as the smallest remaining self-contained domain, preserving every
-required/default member and all existing host implementations before tackling interdependent ADV/input/graphics
-surfaces.
+behavior or the aggregate host accepted by the VM. With diagnostic, lifecycle, and audio contracts established
+beneath `IHost`, introduce the movie host contract next while leaving movie request/graphics transport records in
+their current locations for a separate dependency-cleanup slice; preserve every required/default member and all
+existing host implementations.
 Concrete playthrough blockers may still preempt this bounded maintenance work; the consolidation effort does
 not replace Phase B gameplay validation or the open cross-platform gates.

engine/Age.Engine/Hosting/IAudioHost.cs

@@ -0,0 +1,43 @@
+namespace Age.Engine.Hosting;
+
+public interface IAudioHost
+{
+    void PlayBgm(long id);
+
+    // Ordinary op 0xbf is VM-filtered so reasserting the current track is idempotent. Ops
+    // 0xb7/0xb9 deliberately bypass that guard and restart with logical loop/one-shot mode.
+    void RestartBgm(long id, int startMode) => PlayBgm(id);
+
+    // Op 0xb8 releases the current source rather than merely applying a zero-volume envelope.
+    void StopBgm() => FadeBgm(0, 0);
+
+    void PlayVoice(long id);
+
+    // Native voice playback retains a second start argument: ordinary dialogue passes 0,
+    // while History replay (0x1bd) passes 1. Existing non-audio hosts may ignore it.
+    void PlayVoice(long id, int playbackVariant) => PlayVoice(id);
+
+    void ScheduleVoicePlayback(long id, int playbackVariant, long delayMs) { }
+
+    // Native op 0x1cf stores a transient control mask. Bit 0 suppresses the automatic
+    // BGM attenuation normally applied when a voice starts.
+    void SetVoiceBgmDuckControl(long flags) { }
+
+    void LoadSoundEffect(long resourceId, int channel) { }
+    void StartSoundEffect(int channel) { }
+
+    // Ops 0xb5/0xba share the native channel-start worker. Mode 0 plays once; mode 1
+    // rewinds the decoder at EOF. The one-argument seam remains for simple hosts.
+    void StartSoundEffect(int channel, int startMode) => StartSoundEffect(channel);
+
+    // Native SetDelay (op 0x2bf) starts an already-loaded channel after delayMs.
+    // startMode is forwarded to the same worker used by immediate SFX starts.
+    void ScheduleSoundEffectStart(int channel, int startMode, long delayMs) { }
+
+    void ReleaseSoundEffect(int channel) { }
+    void FadeBgm(int targetPercent, long durationMs) { }
+
+    // AGE's sound:* settings registry is VM-owned; the host applies changes to active playback.
+    void ApplyAudioVolume(int category, int basisPoints) { }
+    void ApplyAudioRouteEnabled(int category, bool enabled) { }
+}

engine/Age.Engine/Hosting/IHost.cs

@@ -48,7 +48,7 @@ public enum SurfaceBlackFadeDirection
     ToBlack,
 }
 
-public interface IHost : IDiagnosticHost, ILifecycleHost
+public interface IHost : IDiagnosticHost, ILifecycleHost, IAudioHost
 {
     /// <summary>Present AGERc's modal full-width editor. Cancel preserves CurrentText.</summary>
     FullwidthTextEditResult EditFullwidthString(FullwidthTextEditRequest request)
@@ -171,33 +171,6 @@ public interface IHost : IDiagnosticHost, ILifecycleHost
     }
     void DrawTexture(int slot, int srcX, int srcY, int width, int height, int dstX, int dstY);
     (int Width, int Height) GetTextureSize(int slot);
-    void PlayBgm(long id);
-    // Ordinary op 0xbf is VM-filtered so reasserting the current track is idempotent. Ops
-    // 0xb7/0xb9 deliberately bypass that guard and restart with logical loop/one-shot mode.
-    void RestartBgm(long id, int startMode) => PlayBgm(id);
-    // Op 0xb8 releases the current source rather than merely applying a zero-volume envelope.
-    void StopBgm() => FadeBgm(0, 0);
-    void PlayVoice(long id);
-    // Native voice playback retains a second start argument: ordinary dialogue passes 0,
-    // while History replay (0x1bd) passes 1. Existing non-audio hosts may ignore it.
-    void PlayVoice(long id, int playbackVariant) => PlayVoice(id);
-    void ScheduleVoicePlayback(long id, int playbackVariant, long delayMs) { }
-    // Native op 0x1cf stores a transient control mask. Bit 0 suppresses the automatic
-    // BGM attenuation normally applied when a voice starts.
-    void SetVoiceBgmDuckControl(long flags) { }
-    void LoadSoundEffect(long resourceId, int channel) { }
-    void StartSoundEffect(int channel) { }
-    // Ops 0xb5/0xba share the native channel-start worker. Mode 0 plays once; mode 1
-    // rewinds the decoder at EOF. The one-argument seam remains for simple hosts.
-    void StartSoundEffect(int channel, int startMode) => StartSoundEffect(channel);
-    // Native SetDelay (op 0x2bf) starts an already-loaded channel after delayMs.
-    // startMode is forwarded to the same worker used by immediate SFX starts.
-    void ScheduleSoundEffectStart(int channel, int startMode, long delayMs) { }
-    void ReleaseSoundEffect(int channel) { }
-    void FadeBgm(int targetPercent, long durationMs) { }
-    // AGE's sound:* settings registry is VM-owned; the host applies changes to active playback.
-    void ApplyAudioVolume(int category, int basisPoints) { }
-    void ApplyAudioRouteEnabled(int category, bool enabled) { }
     // Native op 0x236 binds a movie decoder to an existing retained texture surface.
     // Playback is non-modal: the VM advances to the following instruction while the host publishes frames.
     /// <returns>The initialized movie graph's stop position in truncated integer milliseconds, or null