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.People.Tests/OpinionStoreTests.cs

@@ -0,0 +1,56 @@
+namespace HSchool.People.Tests;
+
+public class OpinionStoreTests
+{
+    [Fact]
+    public void SetZero_RemovesTheEntry()
+    {
+        var person = Blank("a");
+        Assert.True(OpinionStore.Set(person, "b", 12));
+        Assert.Equal(12, OpinionStore.Get(person, "b"));
+
+        Assert.True(OpinionStore.Set(person, "b", 0));
+        Assert.Null(OpinionStore.Get(person, "b"));
+        Assert.False(person.Opinions.ContainsKey("b"));
+    }
+
+    [Fact]
+    public void Set_ClampsToMinusOneHundredAndOneHundred()
+    {
+        var person = Blank("a");
+        OpinionStore.Set(person, "b", 500);
+        Assert.Equal(100, person.Opinions["b"]);
+        OpinionStore.Set(person, "b", -500);
+        Assert.Equal(-100, person.Opinions["b"]);
+    }
+
+    private static Person Blank(string id)
+    {
+        var cases = new CaseTable
+        {
+            Nom = id,
+            Gen = id,
+            Dat = id,
+            Acc = id,
+            Ins = id,
+            Pre = id,
+        };
+        return new Person
+        {
+            Id = id,
+            FamilyId = "f",
+            Female = false,
+            BirthDate = new DateTime(2000, 1, 1, 0, 0, 0, DateTimeKind.Utc),
+            Name = new PersonName(id, id, id, cases, cases, cases),
+            IsStudent = true,
+            IsStaff = false,
+            IsParent = false,
+            Numbers = new Dictionary<string, int>(StringComparer.Ordinal),
+            Choices = new Dictionary<string, string>(StringComparer.Ordinal),
+            Skills = new Dictionary<string, int>(StringComparer.Ordinal),
+            Traits = [],
+            Needs = new Dictionary<string, float>(StringComparer.Ordinal),
+            Opinions = new Dictionary<string, int>(StringComparer.Ordinal),
+        };
+    }
+}