Add EventDef notices, morning and lesson bells, and info toasts.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Simulation/EventSystem.cs

@@ -0,0 +1,48 @@
+using HSchool.Content;
+
+namespace HSchool.Simulation;
+
+/// <summary>
+/// Turns clock edges into world facts. One dayStart per morning crossing, one lessonStart per
+/// school when the bell enters a lesson period — not one per class.
+/// </summary>
+internal static class EventSystem
+{
+    public static IReadOnlyList<WorldEvent> Detect(School school, DateTime before, DateTime after)
+    {
+        if (school.Catalog is null || after <= before)
+        {
+            return [];
+        }
+
+        var facts = new List<WorldEvent>(2);
+        if (CrossedWorkMorning(school.Catalog, before, after, school.SchoolWeekDays))
+        {
+            facts.Add(new WorldEvent(EventTriggers.DayStart));
+        }
+
+        if (EnteredLessonPeriod(school.Catalog, before, after, school.SchoolWeekDays))
+        {
+            facts.Add(new WorldEvent(EventTriggers.LessonStart));
+        }
+
+        return facts;
+    }
+
+    private static bool CrossedWorkMorning(DefCatalog catalog, DateTime before, DateTime after, int weekDays)
+    {
+        if (!PersonDayLog.CrossedDayStart(before, after))
+        {
+            return false;
+        }
+
+        return SchoolDay.IsWorkday(catalog, after, weekDays);
+    }
+
+    private static bool EnteredLessonPeriod(DefCatalog catalog, DateTime before, DateTime after, int weekDays)
+    {
+        var beforeSlot = SchoolDay.At(catalog, before, weekDays);
+        var afterSlot = SchoolDay.At(catalog, after, weekDays);
+        return afterSlot.Kind == DaySlotKind.Lesson && beforeSlot != afterSlot;
+    }
+}

src/HSchool.Simulation/School.cs

@@ -18,6 +18,7 @@ public sealed class School : IDisposable
     private bool _disposed;
     private readonly List<PersonLogEvent> _dayLog = [];
     private readonly HashSet<string> _lessonLogOnce = new(StringComparer.Ordinal);
+    private readonly List<WorldEvent> _worldEvents = [];
 
     internal School(int id, string name, DateTime startDate, DefCatalog? catalog, MapLayout? map)
     {
@@ -297,6 +298,7 @@ public sealed class School : IDisposable
         NeedDecay.Apply(World, Catalog, (next.Value - before).TotalMinutes);
         peopleChanged |= ApparelWear.Apply(this, gameMinutes: 0, before);
         SyncWeather(force: true);
+        RecordWorldEvents(before, next.Value);
         return new SkipEmptyResult(SkipEmptyError.None, next.Value, peopleChanged);
     }
 
@@ -368,6 +370,8 @@ public sealed class School : IDisposable
                 var heavyMinutes = ClockSpeed.HeavyGameMinutes(Clock.SpeedIndex, gameMinutes);
                 peopleChanged |= ApplyHeavySystems(heavyMinutes);
             }
+
+            RecordWorldEvents(before, Clock.Time);
         }
         else
         {
@@ -377,6 +381,24 @@ public sealed class School : IDisposable
         return peopleChanged;
     }
 
+    /// <summary>Facts raised since the last drain. The worker maps them to notices; simulation has no UI.</summary>
+    public IReadOnlyList<WorldEvent> DrainWorldEvents()
+    {
+        if (_worldEvents.Count == 0)
+        {
+            return [];
+        }
+
+        var copy = _worldEvents.ToArray();
+        _worldEvents.Clear();
+        return copy;
+    }
+
+    private void RecordWorldEvents(DateTime before, DateTime after)
+    {
+        _worldEvents.AddRange(EventSystem.Detect(this, before, after));
+    }
+
     private bool ApplyHeavySystems(double gameMinutes)
     {
         HeavySystemsInvocations++;

src/HSchool.Simulation/WorldEvent.cs

@@ -0,0 +1,6 @@
+namespace HSchool.Simulation;
+
+/// <summary>
+/// A fact the school raised this step. Same seam as <c>AffinityEvent</c>: a list, no UI.
+/// </summary>
+public readonly record struct WorldEvent(string Trigger);