Enhance school day structure and decision-making for lunch breaks

- Updated `ai.md` to clarify the mechanics of hunger restoration and the importance of lunch breaks in the school schedule.
- Revised `schedule.md` to detail the new lunch break structure, allowing for separate sittings for different grade levels.
- Enhanced `Decision.cs` and `DecisionPlanner.cs` to incorporate logic for lunch breaks, ensuring that students only leave lessons during their designated lunch windows.
- Updated `DayFrameDef` and related classes to support multiple lunch breaks and validate their configurations.
- Adjusted tests to validate the new decision-making logic regarding lunch breaks and hunger management, ensuring robust functionality.
- Improved localization strings to reflect changes in the school day structure and lunch functionalities.

tests/HSchool.People.Tests/SkillGrantTests.cs

@@ -129,6 +129,37 @@ public class SkillGrantTests
             });
     }
 
+    /// <summary>
+    /// A school saved before native languages carries no pick, and the reload path asks for one
+    /// with <c>rollIfOmitted: false</c>. The contract is that it takes the first listed language
+    /// instead of rolling — a roll would change an existing school's tongue on the next start,
+    /// and the intake after it would draw different people.
+    /// </summary>
+    [Fact]
+    public void ReloadWithoutASavedPick_TakesTheFirstLanguageInsteadOfRolling()
+    {
+        var names = Fixtures.Catalog().NameSets["Slavic"];
+        Assert.True(names.Spoken.Count > 1, "this pins behaviour that only matters for a multi-language set");
+
+        foreach (var seed in new[] { 1, 2, 7, 20260818 })
+        {
+            Assert.Equal(names.Spoken[0], NativeLanguages.Pick(names, seed, requested: null, rollIfOmitted: false));
+        }
+
+        // A new school rolls instead, and the roll is stable for one seed.
+        var rolled = NativeLanguages.Pick(names, 7, requested: null, rollIfOmitted: true);
+        Assert.Contains(rolled, names.Spoken);
+        Assert.Equal(rolled, NativeLanguages.Pick(names, 7, requested: null, rollIfOmitted: true));
+
+        // A saved pick is honoured whichever way it is asked for.
+        Assert.Equal(
+            names.Spoken[^1],
+            NativeLanguages.Pick(names, 7, names.Spoken[^1], rollIfOmitted: false));
+
+        // Anything outside the set comes back null so the create path can answer 400.
+        Assert.Null(NativeLanguages.Pick(names, 7, "Klingon", rollIfOmitted: true));
+    }
+
     [Fact]
     public void OmittedNativeLanguage_IsStableForTheSameSeed()
     {