Enhance apparel definitions: Introduce 'UpperUnderwear' layer and related items (Bra, SportsBra, SoftBra) to support gender-specific clothing. Update inventory and dress generation logic to accommodate new layers and ensure proper coverage. Adjust localization for new apparel terms and refine tests for underwear functionality.

src/HSchool.Content/Defs.cs

@@ -78,6 +78,12 @@ public sealed class ThingDef : Def
     /// <summary>Layers this occupies when worn. Empty — not apparel, so it can sit on the map.</summary>
     public IReadOnlyList<string> Layers { get; init; } = [];
 
+    /// <summary>
+    /// Worn layers fully hidden beneath this piece while condition stays above torn.
+    /// Example: pants list <see cref="ApparelLayers.Underwear"/>.
+    /// </summary>
+    public IReadOnlyList<string> FullyCoversLayers { get; init; } = [];
+
     /// <summary>Can live in a bag, locker or at home. Furniture stays false.</summary>
     public bool Portable { get; init; }