Implement per-school save functionality by introducing a dedicated save directory and updating the school management system to support loading and saving school states. Revise documentation to reflect these changes, including updates to the architecture and design documents, and enhance the API for reloading schools from disk. Update tests to ensure proper functionality of the new save and reload features.

src/HSchool.AppHost/AppHost.cs

@@ -9,6 +9,15 @@ var server = builder.AddProject<Projects.HSchool_Server>("server")
 // Integration tests and CI run headless: no Node, no dev server, just the game server.
 var headless = builder.Configuration.GetValue("HSchool:Headless", false);
 
+if (headless)
+{
+    // Unique folder per AppHost boot so a crashed previous run cannot fill the school limit.
+    var saves = Path.Combine(Path.GetTempPath(), "h-school-tests", Guid.NewGuid().ToString("N"));
+    server
+        .WithEnvironment("Simulation__SavesDirectory", saves)
+        .WithEnvironment("HSchool__AllowSaveReload", "true");
+}
+
 if (!headless)
 {
     var client = builder.AddViteApp("client", "../HSchool.Client")