test: separate non-hermetic release lanes

tests/AcDream.App.Tests/UI/Layout/RetailLayoutFixtureGenerator.cs

@@ -9,9 +9,10 @@ namespace AcDream.App.Tests.UI.Layout;
 
 /// <summary>
 /// Regenerates every committed retail layout fixture from production portal.dat.
-/// The test is inert unless <c>ACDREAM_REGENERATE_UI_FIXTURES=1</c> is set, keeping
+/// The manual lane requires <c>ACDREAM_REGENERATE_UI_FIXTURES=1</c>, keeping
 /// normal test runs deterministic and dat-independent.
 /// </summary>
+[Trait("Lane", "Manual")]
 public sealed class RetailLayoutFixtureGenerator
 {
     private static readonly (uint Id, string FileName)[] Layouts =
@@ -46,7 +47,10 @@ public sealed class RetailLayoutFixtureGenerator
                 "1",
                 StringComparison.Ordinal))
         {
-            return;
+            throw new InvalidOperationException(
+                "Manual fixture generation was not requested; set "
+                    + "ACDREAM_REGENERATE_UI_FIXTURES=1 and ACDREAM_DAT_DIR, "
+                    + "then run the Manual lane explicitly.");
         }
 
         var datDir = Environment.GetEnvironmentVariable("ACDREAM_DAT_DIR")