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,

src/AcDream.App/Rendering/GameWindowLifetime.cs

@@ -118,6 +118,7 @@ internal sealed record RenderShutdownRoots(
     WbMeshAdapter? MeshAdapter,
     Shader? MeshShader,
     TerrainModernRenderer? Terrain,
+    Shader? TerrainShader,
     SceneLightingUboBinding? SceneLighting,
     DebugLineRenderer? DebugLines,
     TextRenderer? TextRenderer,
@@ -454,6 +455,7 @@ internal static class GameWindowShutdownManifest
             [
                 Hard("mesh shader", () => render.MeshShader?.Dispose()),
                 Hard("terrain", () => render.Terrain?.Dispose()),
+                Hard("terrain shader", () => render.TerrainShader?.Dispose()),
                 Hard("scene lighting", () => render.SceneLighting?.Dispose()),
                 Hard("debug lines", () => render.DebugLines?.Dispose()),
                 Hard("text renderer", () => render.TextRenderer?.Dispose()),

src/AcDream.App/Rendering/Shaders/terrain_modern.frag

@@ -30,26 +30,15 @@ out vec4 fragColor;
 // Campaign V slice V2b (2026-07-27): uTerrainHandle/uAlphaHandle (uvec2, raw
 // ARB_bindless_texture handles) became uTextureIndexA/uTextureIndexB (slots
 // into the binding=9 handle table, ACDREAM_TEXTURE_HANDLE in common.glsl).
-// Named to match the pinned GpuPushConstants.TextureIndexA/B fields, so slice
-// V4d's move onto push constants was a rename rather than a redesign. The GL
-// backend maps each push-constant field to the correspondingly named uniform,
-// which is why these stay declared exactly as they are.
+// Named to match the pinned GpuPushConstants.TextureIndexA/B fields so V4d's
+// move to push constants is a rename, not a redesign — there is no
+// push-constant plumbing yet, so these stay plain uniforms for now.
 uniform uint uTextureIndexA;
 uniform uint uTextureIndexB;
+uniform float uTexTiling[36];
 #define uTerrain sampler2DArray(ACDREAM_TEXTURE_HANDLE(uTextureIndexA))
 #define uAlpha   sampler2DArray(ACDREAM_TEXTURE_HANDLE(uTextureIndexB))
 
-// Campaign V slice V4d: the per-layer tiling table moved out of a loose
-// `uniform float uTexTiling[36]` and into a uniform block at
-// GpuBindingModel.UniformTerrainTiling. At 144 bytes of payload it cannot ride
-// in the 96-byte GpuPushConstants block (nor Vulkan's guaranteed 128-byte
-// ceiling), and there is no RHI verb for setting a uniform array. std140 pads
-// each array element to 16 bytes, so the block is 576 bytes; the element type
-// is unchanged so uTexTiling[i] reads exactly as it did before.
-layout(std140, ACDREAM_UBO_SET binding = 3) uniform TerrainTiling {
-    float uTexTiling[36];
-};
-
 struct Light {
     vec4 posAndKind;
     vec4 dirAndRange;