app: wire Serilog into SVSim.EmulatedEntrypoint

Registers Serilog via SVSim.Hosting.UseSvSimSerilog("svsim-api") right
after CreateBuilder and wraps Main in try/catch/finally so a fatal
startup exception logs before CloseAndFlush.

Also updates the SVSim.Hosting extension to gate the file sink on entry
assembly rather than the ASP.NET environment name. WebApplicationFactory
sets the environment via a hook that resolves after both CreateBuilder
and the UseSerilog callback see their environment view, so
IsEnvironment("Testing") is unreliable in tests. The entry assembly
under `dotnet test` is always "testhost", which is a reliable signal.

appsettings.json grows a Serilog section mirroring the existing
Logging:LogLevel overrides; the Logging block itself is left in place
per the spec's follow-up cleanup note.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Program.cs

@@ -20,6 +20,8 @@ using SVSim.EmulatedEntrypoint.Middlewares;
 using SVSim.EmulatedEntrypoint.Security.SteamSessionAuthentication;
 using SVSim.EmulatedEntrypoint.Services;
 using SVSim.BattleNode.Hosting;
+using Serilog;
+using SVSim.Hosting;
 
 namespace SVSim.EmulatedEntrypoint;
 
@@ -29,6 +31,13 @@ public class Program
     {
         var builder = WebApplication.CreateBuilder(args);
 
+        // Always register Serilog. The file sink self-gates on the Testing environment inside
+        // the UseSvSimSerilog callback — a caller-side check here would be too early because
+        // WebApplicationFactory applies UseEnvironment("Testing") after CreateBuilder returns.
+        builder.Host.UseSvSimSerilog("svsim-api");
+
+        try
+        {
         // Add services to the container.
 
         builder.Services.AddControllers().AddJsonOptions(opt =>
@@ -253,5 +262,15 @@ public class Program
         app.MapControllers();
 
         app.Run();
+        }
+        catch (Exception ex)
+        {
+            Log.Fatal(ex, "Host terminated unexpectedly");
+            throw;
+        }
+        finally
+        {
+            Log.CloseAndFlush();
+        }
     }
 }

SVSim.EmulatedEntrypoint/SVSim.EmulatedEntrypoint.csproj

@@ -39,6 +39,7 @@
   <ItemGroup>
     <ProjectReference Include="..\SVSim.Database\SVSim.Database.csproj" />
     <ProjectReference Include="..\SVSim.BattleNode\SVSim.BattleNode.csproj" />
+    <ProjectReference Include="..\SVSim.Hosting\SVSim.Hosting.csproj" />
   </ItemGroup>
 
   <ItemGroup>

SVSim.EmulatedEntrypoint/appsettings.json

@@ -9,6 +9,18 @@
       "Microsoft.EntityFrameworkCore.Infrastructure": "Warning"
     }
   },
+  "Serilog": {
+    "MinimumLevel": {
+      "Default": "Information",
+      "Override": {
+        "Microsoft.AspNetCore": "Warning",
+        "Microsoft.AspNetCore.HttpLogging.HttpLoggingMiddleware": "Information",
+        "Microsoft.EntityFrameworkCore": "Warning",
+        "Microsoft.EntityFrameworkCore.Database.Command": "Warning",
+        "Microsoft.EntityFrameworkCore.Infrastructure": "Warning"
+      }
+    }
+  },
   "ConnectionStrings": {
     "ApplicationDb": "Host=localhost;Database=svsim;Username=postgres;password=postgres"
   },

SVSim.Hosting/SerilogHostingExtensions.cs

@@ -1,3 +1,4 @@
+using System.Reflection;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Hosting;
 using Serilog;
@@ -8,6 +9,14 @@ namespace SVSim.Hosting;
 
 public static class SerilogHostingExtensions
 {
+    // Detects `dotnet test` runs regardless of ASPNETCORE_ENVIRONMENT wiring. The env check
+    // via HostingEnvironment.IsEnvironment("Testing") is unreliable here because
+    // WebApplicationFactory<TEntryPoint> sets the environment via a mechanism that fires after
+    // both CreateBuilder and the UseSerilog callback resolve their environment view. The entry
+    // assembly under NUnit + dotnet test is always "testhost" or "testhost.x86".
+    private static readonly bool IsTestHost =
+        Assembly.GetEntryAssembly()?.GetName().Name?.StartsWith("testhost", StringComparison.OrdinalIgnoreCase) == true;
+
     // Wires Serilog as the host's logging provider. Sinks, rotation, retention,
     // and enrichment defaults are baked in here; per-category level overrides
     // ride via appsettings under "Serilog:MinimumLevel:Override". The file sink
@@ -28,15 +37,23 @@ public static class SerilogHostingExtensions
                 .Enrich.WithThreadId()
                 .WriteTo.Console(
                     theme: AnsiConsoleTheme.Code,
-                    outputTemplate: "[{Timestamp:HH:mm:ss} {Level:u3}] {SourceContext} {Message:lj}{NewLine}{Exception}")
-                .WriteTo.File(
+                    outputTemplate: "[{Timestamp:HH:mm:ss} {Level:u3}] {SourceContext} {Message:lj}{NewLine}{Exception}");
+
+            // Skip the file sink under `dotnet test` so unit-test runs don't scatter log files
+            // under SVSim.UnitTests/bin/. See IsTestHost above for why we detect via entry
+            // assembly instead of the ASP.NET environment name.
+            if (!IsTestHost)
+            {
+                loggerConfig.WriteTo.File(
                     path: filePathBase,
                     rollingInterval: RollingInterval.Day,
                     rollOnFileSizeLimit: true,
                     fileSizeLimitBytes: 100_000_000,
                     retainedFileCountLimit: 7,
-                    outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {SourceContext} {Message:lj}{NewLine}{Exception}")
-                .ReadFrom.Configuration(context.Configuration);
+                    outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {SourceContext} {Message:lj}{NewLine}{Exception}");
+            }
+
+            loggerConfig.ReadFrom.Configuration(context.Configuration);
         });
     }
 }