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>

tests/HSchool.Simulation.Tests/TalkCircleTests.cs

@@ -151,6 +151,28 @@ public class TalkCircleTests
         }
     }
 
+    [Fact]
+    public void TalkCircleFinish_MarksTickPeopleChangedSoSaveWritesOpinions()
+    {
+        var (school, first, second) = TwoPupilsOnBreak();
+        using (school)
+        {
+            OpinionStore.Set(first, second.Id, 10);
+            PlaceAt(school, first.Id, "corridor-1");
+            PlaceAt(school, second.Id, "corridor-1");
+            Assert.True(school.TryStartAction(first.Id, TalkActions.Chat));
+
+            var peopleChanged = false;
+            while (ActivityOf(school, first.Id) is not null)
+            {
+                peopleChanged |= school.Tick(0.2d, 5d);
+            }
+
+            Assert.True(peopleChanged);
+            Assert.NotEqual(10, OpinionStore.Get(first, second.Id));
+        }
+    }
+
     private static (School School, Person First, Person Second) TwoPupilsWithPhonesOnBreak()
     {
         var (catalog, map) = Vanilla();