Add HSchool.Content project for JSONC definitions, catalog, and map validation. Update solution structure to include new content and tests projects. Enhance school management to support mod packs and map instances, ensuring proper loading and validation. Revise documentation to reflect these changes and update tests for new functionality.

README.md

@@ -74,6 +74,7 @@ dotnet test
 ```
 
 - `tests/HSchool.Protocol.Tests` — wire-format round-trips and byte layouts.
+- `tests/HSchool.Content.Tests` — JSONC catalog, inheritance, patches, map connectivity. No host.
 - `tests/HSchool.Simulation.Tests` — the game clock, school load/create, and the school registry, no host involved.
 - `tests/HSchool.AppHost.Tests` — boots the real Aspire graph, drives the menu API and the
   WebSocket clock. Runs headless (`--HSchool:Headless=true`), so no Node install is needed.
@@ -89,8 +90,10 @@ Vitest covers the client codec, the calendar formatting and the RU/EN dictionari
 ```
 src/
   HSchool.Protocol/        binary wire format (shared contract with the client)
+  HSchool.Content/         JSONC defs, patches, map validation
   HSchool.Simulation/      schools, the game clock, the Arch ECS world
-  HSchool.Server/          ASP.NET Core host, menu API, WebSocket endpoint, game loop
+  HSchool.Server/          ASP.NET Core host, menu API, WebSocket, workers
+  HSchool.Server/mods/     pack folders; `core` is always on
   HSchool.ServiceDefaults/ Aspire telemetry, health checks, resilience
   HSchool.AppHost/         Aspire orchestration
   HSchool.Client/          Vite + TypeScript UI
@@ -112,9 +115,12 @@ Simulation tunables live under the `Simulation` section of
 | `MaxSchools` | 6 | how many schools may exist at once |
 | `GameMinutesPerRealSecond` | 5 | game minutes per real second at ×1 |
 | `DefaultStartDate` | `2012-04-03T06:00:00` | prefilled start of a new school |
+| `SavesDirectory` | `saves` | per-school JSON files |
+| `ModsDirectory` | `mods` | pack folders; `core` is required |
+| `SaveIntervalSeconds` | 30 | rare clock snapshot; not every tick |
 
 ## What is deliberately missing
 
-No persistence, no authentication, and nothing inside a school yet — every school owns an empty
-ECS world waiting for its first entities. Each of these has a seam described in
+No authentication, no action execution, and the create dialog does not yet pick mods or edit the
+map — every new school gets the vanilla `core` layout. Each of these has a seam described in
 [`docs/architecture.md`](docs/architecture.md).