NEO-38: set integration test host to Testing for deterministic JSON errors

server/NeonSprawl.Server.Tests/Game/PositionState/PostgresWebApplicationFactory.cs

@@ -18,6 +18,8 @@ public sealed class PostgresWebApplicationFactory : WebApplicationFactory<Progra
                 "Set ConnectionStrings__NeonSprawl for Postgres integration tests (see server/README.md).");
         }
 
+        builder.UseEnvironment("Testing");
+
         var skillsDir = SkillCatalogPathResolution.TryDiscoverSkillsDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/skills from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");

server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs

@@ -19,6 +19,10 @@ public sealed class InMemoryWebApplicationFactory : WebApplicationFactory<Progra
 
     protected override void ConfigureWebHost(IWebHostBuilder builder)
     {
+        // Avoid Development + DeveloperExceptionPage: invalid JSON / binding failures must stay 400 for API tests,
+        // and Release CI runs rely on deterministic status codes (e.g. HotbarLoadoutApiTests malformed-body case).
+        builder.UseEnvironment("Testing");
+
         var skillsDir = SkillCatalogPathResolution.TryDiscoverSkillsDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/skills from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");