Persist talk opinions and pick topics by weight.

A finished circle never set Tick's peopleChanged bit, so people.json kept pre-talk numbers until morning drift. PickTopic compared a 0..total roll to a 0..1 cursor, so gossip almost never changed the subject.

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

src/HSchool.Simulation/School.cs

@@ -136,6 +136,12 @@ public sealed class School : IDisposable
 
     internal Dictionary<string, string> TalkCircleByPerson { get; } = new(StringComparer.Ordinal);
 
+    /// <summary>
+    /// A finished or interrupted circle wrote opinions onto the roster. <see cref="Tick"/>
+    /// returns this so the worker persists <c>people.json</c> — same seam as morning dress.
+    /// </summary>
+    internal bool RosterTalkDirty { get; set; }
+
     internal void ResetDayLog()
     {
         _dayLog.Clear();
@@ -397,6 +403,8 @@ public sealed class School : IDisposable
             peopleChanged |= AffinitySystem.Apply(this, talked);
         }
 
+        peopleChanged |= RosterTalkDirty;
+        RosterTalkDirty = false;
         return peopleChanged;
     }
 

src/HSchool.Simulation/TalkCircleSystem.cs

@@ -457,6 +457,7 @@ internal static class TalkCircleSystem
         }
 
         school.TalkCirclesById.Remove(circle.Id);
+        school.RosterTalkDirty = true;
     }
 
     private static bool TryCatchWhisper(School school, ActiveTalkCircle circle)