Revert "feat(render): Campaign V slice V4d-2 - move terrain onto the RHI"

This reverts commit b064668b63.

src/AcDream.App/Rendering/GameWindow.cs

@@ -48,6 +48,9 @@ public sealed class GameWindow :
     private GL? _gl;
     private IInputContext? _input;
     private TerrainModernRenderer? _terrain;
+    /// <summary>Phase N.5b: terrain_modern.vert/.frag program. Owned by
+    /// <see cref="_terrain"/> at draw time but allocated + disposed here.</summary>
+    private Shader? _terrainModernShader;
     private CameraController? _cameraController;
     private IDatReaderWriter? _dats;
     private IPreparedAssetSource? _preparedAssets;
@@ -894,6 +897,12 @@ public sealed class GameWindow :
             value,
             "bindless support");
 
+    void IGameWindowWorldRenderPublication.PublishTerrainShader(Shader value) =>
+        PublishCompositionOwner(
+            ref _terrainModernShader,
+            value,
+            "terrain shader");
+
     void IGameWindowWorldRenderPublication.PublishSceneLighting(
         SceneLightingUboBinding value) =>
         PublishCompositionOwner(
@@ -1672,6 +1681,7 @@ public sealed class GameWindow :
             _wbMeshAdapter,
             _meshShader,
             _terrain,
+            _terrainModernShader,
             _sceneLightingUbo,
             _debugLines,
             _textRenderer,