Enhance school simulation and management by integrating roster functionality, allowing for the installation and persistence of student and staff data. Update the school architecture to include a roster alongside existing components, ensuring proper validation against map layouts. Revise room definitions to support homeroom designations and update related tests to validate new functionalities and ensure robustness in roster handling.

docs/architecture.md

@@ -16,8 +16,9 @@ there is no UI on the server.
 │  │    │          ├─ Clock│                                               │
 │  │    │          ├─ Catalog (frozen Content)                             │
 │  │    │          ├─ Map                                                 │
-│  │    │          └─ World│ (Arch ECS, empty for now)                     │
-│  │    ├── SchoolStore     │  saves/{id}.json                             │
+│  │    │          ├─ Roster                                              │
+│  │    │          └─ World│ (Arch ECS: people, classes)                   │
+│  │    ├── SchoolStore     │  saves/{id}.json + {id}.people.json          │
 │  │    ├── ModContent      │  mods/<id>/                                  │
 │  │    └── ClientRegistry  │                                              │
 │  └────────────────────────┘                                              │
@@ -75,9 +76,8 @@ touching a school itself.
 
 ## Schools
 
-A `School` is one save: an id, a name, a `GameClock` and an Arch `World`. The world is empty
-today — pupils, rooms and staff land in it as the game grows — but it is created and destroyed
-with the school so ownership is never in question.
+A `School` is one save: an id, a name, a `GameClock`, a frozen catalog, a map, a roster and an
+Arch `World`. Pupils, staff and parents live in that world as entities; they do not walk yet.
 
 `GameClock` moves while it is running, in fixed steps:
 `realSeconds × gameMinutesPerRealSecond × speedMultiplier`. At the defaults that is 5 game minutes
@@ -97,13 +97,16 @@ cannot land between a mouse-down and a click.
 ## Saves
 
 Each school is a JSON file under `Simulation:SavesDirectory` (`saves/{id}.json` plus `index.json`
-for the next id). The worker writes on create, on shutdown, and on a rare clock snapshot
-(`SaveIntervalSeconds`, 30 by default) — never on every tick. Pause and speed changes are written
+for the next id, and `saves/{id}.people.json` for the roster). The worker writes the clock file on
+create, on shutdown, and on a rare clock snapshot (`SaveIntervalSeconds`, 30 by default) — never
+on every tick. The people file is written only when composition changes (create, and later yearly
+intake). Pause and speed changes are written
 too, but coalesced to at most one write per `MinSaveIntervalMilliseconds`: a client can send those
 as fast as the socket allows, and each one is a file write on the school's own thread. Shutdown
-always flushes, so a pause is never lost. The file also stores the
+always flushes, so a pause is never lost. The clock file also stores the
 mod pack ids and the map layout; the catalog is loaded again from `mods/` on start. A missing
-mod folder or a map that no longer validates leaves the file in place and that school unstarted.
+mod folder, a map that no longer validates, or a roster that no longer fits the map leaves the
+files in place and that school unstarted.
 
 ## Connection lifetime