Fix PE change-clothes interruption and post-PE mode detection.

Add appropriateness tests for staging PE kit, wearing form before gym, and returning to everyday clothes after the lesson.

src/HSchool.Simulation/ActivitySystem.cs

@@ -166,9 +166,10 @@ internal static class ActivitySystem
         ApparelDresser.RedressPerson(school, person, mode, includeHome: false, todaySubjects: subjects);
     }
 
-    private static bool IsChangeClothes(string actionId) =>
-        actionId.Equals(ApparelActions.ChangeMale, StringComparison.Ordinal)
-        || actionId.Equals(ApparelActions.ChangeFemale, StringComparison.Ordinal);
+    internal static bool IsChangeClothes(string? actionId) =>
+        actionId is not null
+        && (actionId.Equals(ApparelActions.ChangeMale, StringComparison.Ordinal)
+            || actionId.Equals(ApparelActions.ChangeFemale, StringComparison.Ordinal));
 
     private static int Occupied(School school, string nodeId, string thing)
     {

src/HSchool.Simulation/ApparelPresence.cs

@@ -56,10 +56,27 @@ internal static class ApparelPresence
             return ApparelDresser.ModeForLesson(current?.Subject);
         }
 
-        var next = lessons.Where(lesson => lesson.Period > slot.Index).OrderBy(lesson => lesson.Period).FirstOrDefault();
-        if (next is not null)
+        if (slot.Kind == DaySlotKind.Break)
         {
-            return ApparelDresser.ModeForLesson(next.Subject);
+            var justEnded = lessons.FirstOrDefault(lesson => lesson.Period == slot.Index);
+            if (justEnded is not null && ApparelDresser.ModeForLesson(justEnded.Subject) == ApparelMode.Pe)
+            {
+                return ApparelMode.Everyday;
+            }
+
+            var next = lessons.Where(lesson => lesson.Period > slot.Index).OrderBy(lesson => lesson.Period).FirstOrDefault();
+            if (next is not null)
+            {
+                return ApparelDresser.ModeForLesson(next.Subject);
+            }
+
+            return ApparelMode.Everyday;
+        }
+
+        var nextLesson = lessons.Where(lesson => lesson.Period > slot.Index).OrderBy(lesson => lesson.Period).FirstOrDefault();
+        if (nextLesson is not null)
+        {
+            return ApparelDresser.ModeForLesson(nextLesson.Subject);
         }
 
         var previous = lessons.Where(lesson => lesson.Period < slot.Index).OrderByDescending(lesson => lesson.Period).FirstOrDefault();

src/HSchool.Simulation/PresenceSystem.cs

@@ -400,15 +400,18 @@ internal static class PresenceSystem
             state,
             (node, thing) => occupied.GetValueOrDefault((node, thing)));
 
+        var changing = activity.IsActive && ActivitySystem.IsChangeClothes(activity.ActionId);
+
         if (decision.WalkTo is not null
             && !decision.WalkTo.Equals(presence.NodeId, StringComparison.Ordinal)
-            && activity.IsActive)
+            && activity.IsActive
+            && !changing)
         {
             activity = PersonActivity.Idle;
         }
 
         intent = decision.Intent;
-        if (decision.WalkTo is not null)
+        if (decision.WalkTo is not null && !changing)
         {
             presence = PresenceStepper.StartWalk(presence, walks, decision.WalkTo, headingHome: false);
         }