Update wire protocol to version 5, introducing pupil slots and item counts in map snapshots. Enhance UI components to display pupil slots and item counts in game screens and map editors. Revise localization strings for improved user guidance. Update tests to validate new functionalities and ensure robustness in handling room and item data.

src/HSchool.Content/Defs.cs

@@ -27,6 +27,12 @@ public sealed class ActionDef : Def;
 public sealed class ThingDef : Def
 {
     public IReadOnlyList<string> Actions { get; init; } = [];
+
+    /// <summary>
+    /// How many pupils this thing hosts for lessons. Zero for teacher's furniture — a chair
+    /// must not inflate class size just because someone sits in it.
+    /// </summary>
+    public int PupilSlots { get; init; }
 }
 
 public sealed class PositionDef : Def;