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

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

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);