Skip users.json when loading school saves.

The session user list sits beside {id}.json; LoadAll treated it as a school with id 0.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/HSchool.Server.Tests/HSchool.Server.Tests.csproj

@@ -15,6 +15,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\HSchool.Server\HSchool.Server.csproj" />
     <ProjectReference Include="..\..\src\HSchool.People\HSchool.People.csproj" />
+    <ProjectReference Include="..\..\src\HSchool.Simulation\HSchool.Simulation.csproj" />
   </ItemGroup>
 
   <ItemGroup>

tests/HSchool.Server.Tests/SchoolStoreTests.cs

@@ -0,0 +1,60 @@
+using HSchool.Server.Game;
+using HSchool.Simulation;
+using Microsoft.Extensions.FileProviders;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+
+namespace HSchool.Server.Tests;
+
+public class SchoolStoreTests
+{
+    [Fact]
+    public void LoadAll_SkipsUsersJsonBesideASchoolSave()
+    {
+        var directory = Directory.CreateTempSubdirectory("h-school-store-");
+        try
+        {
+            File.WriteAllText(
+                Path.Combine(directory.FullName, UserStore.FileName),
+                """{ "users": [ { "name": "Player" } ] }""");
+            File.WriteAllText(
+                Path.Combine(directory.FullName, "1.json"),
+                """
+                {
+                  "format": 3,
+                  "id": 1,
+                  "name": "North",
+                  "gameTime": "2012-03-31T06:00:00Z",
+                  "running": false,
+                  "speedIndex": 0
+                }
+                """);
+
+            var store = CreateStore(directory.FullName);
+            var saves = store.LoadAll();
+
+            var save = Assert.Single(saves);
+            Assert.Equal(1, save.Id);
+            Assert.Equal("North", save.Name);
+        }
+        finally
+        {
+            directory.Delete(recursive: true);
+        }
+    }
+
+    private static SchoolStore CreateStore(string directory)
+    {
+        var options = Options.Create(new SimulationOptions { SavesDirectory = directory });
+        return new SchoolStore(options, new StubHost(), NullLogger<SchoolStore>.Instance);
+    }
+
+    private sealed class StubHost : IHostEnvironment
+    {
+        public string ApplicationName { get; set; } = "HSchool.Server.Tests";
+        public string EnvironmentName { get; set; } = "Development";
+        public string ContentRootPath { get; set; } = Path.GetTempPath();
+        public IFileProvider ContentRootFileProvider { get; set; } = new NullFileProvider();
+    }
+}