merge: bring main (UN-7, #140 filing, D.2b UI rows) into A7 Fix D round-2 branch

Resolves the divergence-register conflict: kept the accurate per-VERTEX AP-35
(Fix A shipped per-vertex; main's row was the stale pre-Fix-A per-pixel text),
kept main's UI rows AP-37..AP-42, and renumbered this branch's torch-gate row
AP-37 -> AP-43 (AP-37 was taken by main's LayoutDesc row). AP count 41 -> 42.
Retargeted the AP-37 references in WbDrawDispatcher + the CHECKPOINT to AP-43.
Marked ISSUES #140 RESOLVED (b7d655b) with the corrected root cause.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Tests/Plugins/PluginLoaderTests.cs

@@ -30,6 +30,12 @@ public class PluginLoaderTests
         public IPluginLogger Log { get; } = new StubLogger();
         public IGameState State { get; } = new StubState();
         public IEvents Events { get; } = new StubEvents();
+        public IUiRegistry Ui { get; } = new StubUiRegistry();
+    }
+
+    private sealed class StubUiRegistry : IUiRegistry
+    {
+        public void AddMarkupPanel(string markupPath, object binding) { }
     }
 
     private sealed class StubLogger : IPluginLogger

tests/AcDream.Core.Tests/Textures/SurfaceDecoderSolidColorTests.cs

@@ -0,0 +1,17 @@
+using AcDream.Core.Textures;
+using Xunit;
+
+namespace AcDream.Core.Tests.Textures;
+
+public class SurfaceDecoderSolidColorTests
+{
+    [Fact]
+    public void DecodeSolidColor_NullColor_ReturnsMagenta_DoesNotThrow()
+    {
+        // A malformed Base1Solid surface can carry a null ColorValue. DecodeSolidColor
+        // is called outside DecodeRenderSurface's try/catch (from TextureCache), so it
+        // must be null-safe itself — return the undecodable sentinel, never NRE.
+        var result = SurfaceDecoder.DecodeSolidColor(null!, 0f);
+        Assert.Equal(DecodedTexture.Magenta, result);
+    }
+}