Split diagnostic and lifecycle host contracts

docs/PROJECT-STRUCTURE.md

@@ -160,6 +160,12 @@ transitions, diagnostic snapshots, frame/completion publication, and mask teardo
 control, and blocking BGM fades; presentation/input retains the message-skip, reset, and frame-pulse consumers
 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.
+
 `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,
 animation, numeric-glyph, and handle-range contracts. `engine/Age.Engine/Model/GfxState.Surfaces.cs` owns surface

docs/remake-architecture-and-roadmap.md

@@ -759,6 +759,12 @@ do not mix mechanical moves with semantic changes.
    headless defaults and diagnostics; interface cleanup must not turn intentionally unsupported presentation
    into false success.
 
+   **Progress (2026-08-03):** the first bounded contract slice introduced `IDiagnosticHost` for recoverable
+   warnings and modal diagnostic messages and `ILifecycleHost` for script-context entry/exit, sleep and timed
+   deadline waiting, frame yield, and scene reset. `IHost` inherits both contracts and remains the aggregate VM
+   entry point; all required members, default implementations, existing hosts, and transport-record locations
+   are 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
@@ -1117,9 +1123,10 @@ layer's rendering diverges from ADV; save layout.
 ---
 
 ## 8. Immediate next step
-Begin step 3 of the **codebase consolidation** maintenance slice: clarify runtime contracts without changing
-behavior or the aggregate host accepted by the VM. Start with a bounded interface-only slice that introduces
-diagnostic and lifecycle host contracts beneath `IHost`, preserving current default implementations and existing
-host classes before separating the larger ADV, graphics, audio, movie, and input surfaces.
+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.
 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/IDiagnosticHost.cs

@@ -0,0 +1,11 @@
+namespace Age.Engine.Hosting;
+
+public interface IDiagnosticHost
+{
+    /// <summary>Report a recoverable runtime discrepancy while allowing script execution to continue.</summary>
+    void ReportWarning(string message) => System.Console.Error.WriteLine(message);
+
+    /// <summary>Present a modal diagnostic and return only after the user dismisses it.</summary>
+    void ShowDiagnosticMessage(DiagnosticMessage message)
+        => System.Console.Error.WriteLine($"{message.Caption}: {message.Text}");
+}

engine/Age.Engine/Hosting/IHost.cs

@@ -48,19 +48,11 @@ public enum SurfaceBlackFadeDirection
     ToBlack,
 }
 
-public interface IHost
+public interface IHost : IDiagnosticHost, ILifecycleHost
 {
-    /// <summary>Report a recoverable runtime discrepancy while allowing script execution to continue.</summary>
-    void ReportWarning(string message) => System.Console.Error.WriteLine(message);
-    /// <summary>Present a modal diagnostic and return only after the user dismisses it.</summary>
-    void ShowDiagnosticMessage(DiagnosticMessage message)
-        => System.Console.Error.WriteLine($"{message.Caption}: {message.Text}");
     /// <summary>Present AGERc's modal full-width editor. Cancel preserves CurrentText.</summary>
     FullwidthTextEditResult EditFullwidthString(FullwidthTextEditRequest request)
         => new(false, request.CurrentText);
-    // Script context is retained for diagnostics/page location; resource operands are universal packed ids.
-    void EnterScriptContext(string scriptName) { }
-    void ExitScriptContext() { }
     void ShowText(int offset, string text);
     void ShowText(AdvLiveTextRun run, int glyphDelayMilliseconds)
         => ShowText(run.SourceOffset, run.Text);
@@ -140,14 +132,6 @@ public interface IHost
     long InputClockMilliseconds => Environment.TickCount64;
     void SetCursorResource(long resourceId) { }
     void ClearCursorResource() { }
-    void Sleep(long duration);
-    // Native op-0xd5 pacing sleeps inside run-state 0x40 without publishing retained gfx state.
-    // Interactive hosts must keep this distinct from presentation-capable script op-0xc8 sleep.
-    void WaitForTimedCallbackDeadline(long duration) => Sleep(duration);
-    void FrameYield();
-    // Native op 0x9 resets scene-owned host services before reloading root script resource 0.
-    // Global banks, engine configuration, decoded-asset caches, and persistent profile state survive.
-    void ResetSceneContext() { }
     // Native 0x1c7/0x1cc query two distinct ADV skip channels. Headless and non-interactive
     // hosts default to normal playback; the Godot host supplies the live interactive values.
     void SetMessageSkipActive(bool active) { }

engine/Age.Engine/Hosting/ILifecycleHost.cs

@@ -0,0 +1,20 @@
+namespace Age.Engine.Hosting;
+
+public interface ILifecycleHost
+{
+    // Script context is retained for diagnostics/page location; resource operands are universal packed ids.
+    void EnterScriptContext(string scriptName) { }
+    void ExitScriptContext() { }
+
+    void Sleep(long duration);
+
+    // Native op-0xd5 pacing sleeps inside run-state 0x40 without publishing retained gfx state.
+    // Interactive hosts must keep this distinct from presentation-capable script op-0xc8 sleep.
+    void WaitForTimedCallbackDeadline(long duration) => Sleep(duration);
+
+    void FrameYield();
+
+    // Native op 0x9 resets scene-owned host services before reloading root script resource 0.
+    // Global banks, engine configuration, decoded-asset caches, and persistent profile state survive.
+    void ResetSceneContext() { }
+}