Give each school its own people seed so composition no longer follows create order.

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

tests/HSchool.AppHost.Tests/PeopleApiTests.cs

@@ -139,14 +139,14 @@ public class PeopleApiTests(AppHostFixture fixture)
     {
         using var client = fixture.App.CreateHttpClient("server");
         await SchoolApiTests.ResetAsync(client);
-        var school = await SchoolApiTests.CreateAsync(client, "Люди семья", Start);
+        var school = await SchoolApiTests.CreateAsync(client, "Люди семья", Start, seed: 1);
 
         var page = await GetPeopleAsync(client, school.Id, "role=student&year=5&pageSize=10");
 
-        // Every fifth-to-tenth family is single-parent on purpose (design/people.md), and the
-        // roster seed is the school id — which depends on how many schools ran before this test.
-        // Demanding two parents from whoever happens to sort first therefore fails on some runs;
-        // look for a pupil who has a mother instead of assuming the first one does.
+        // Every fifth-to-tenth family is single-parent on purpose (design/people.md). The roster
+        // seed is no longer the school id, but a given page still mixes complete and single-parent
+        // houses, so demanding two parents from whoever sorts first fails on some seeds. Look for
+        // a pupil who has a mother instead of assuming the first one does.
         PersonCardResponse? card = null;
         foreach (var candidate in page.People)
         {