Add timetable planning and related tests to school simulation

- Introduced a new project for timetable planning, dependent on HSchool.Content.
- Updated documentation to reflect the addition of timetable planning and its dependencies.
- Added tests for timetable planning to ensure deterministic behavior with the same staff and map.
- Revised architecture documentation to include the new HSchool.Schedule component and its interactions.

tests/HSchool.Schedule.Tests/Fixtures.cs

@@ -0,0 +1,112 @@
+using HSchool.Content;
+
+namespace HSchool.Schedule.Tests;
+
+internal static class PackDocuments
+{
+    public static IReadOnlyList<ContentDocument> FromDirectory(string packId, string packRoot)
+    {
+        var documents = new List<ContentDocument>();
+        foreach (var path in Directory.EnumerateFiles(packRoot, "*.*", SearchOption.AllDirectories))
+        {
+            if (!path.EndsWith(".jsonc", StringComparison.OrdinalIgnoreCase)
+                && !path.EndsWith(".json", StringComparison.OrdinalIgnoreCase))
+            {
+                continue;
+            }
+
+            var relative = Path.GetRelativePath(packRoot, path).Replace('\\', '/');
+            documents.Add(new ContentDocument(packId, relative, File.ReadAllText(path)));
+        }
+
+        return documents;
+    }
+}
+
+internal static class Fixtures
+{
+    public static DefCatalog Catalog()
+    {
+        var root = Path.Combine(AppContext.BaseDirectory, "vanilla");
+        return new CatalogLoader().Load(
+            [CatalogLoader.CorePackId],
+            PackDocuments.FromDirectory(CatalogLoader.CorePackId, root));
+    }
+
+    public static MapLayout ClassroomsAndGym(int classes, int desks = 16)
+    {
+        var rooms = new List<RoomNode>(classes + 1);
+        for (var i = 0; i < classes; i++)
+        {
+            rooms.Add(Classroom(i, desks));
+        }
+
+        rooms.Add(new RoomNode
+        {
+            Id = "gym-hall",
+            Def = "GymHall",
+            Building = "gym",
+            Floor = "gym-floor",
+            Slots = [new SlotFill { Key = "benches", Thing = "Bench", Count = 4 }],
+        });
+
+        return new MapLayout { Rooms = rooms };
+    }
+
+    public static MapLayout ClassroomAndLab(int desks = 16, int computers = 12)
+    {
+        return new MapLayout
+        {
+            Rooms =
+            [
+                Classroom(0, desks),
+                new RoomNode
+                {
+                    Id = "computer-lab",
+                    Def = "ComputerLab",
+                    Building = "main",
+                    Floor = "floor-1",
+                    Slots =
+                    [
+                        new SlotFill { Key = "teacherDesk", Thing = "Desk", Count = 1 },
+                        new SlotFill { Key = "teacherChair", Thing = "Chair", Count = 1 },
+                        new SlotFill { Key = "computers", Thing = "Computer", Count = computers },
+                    ],
+                },
+            ],
+        };
+    }
+
+    public static PlannerClass Class(int index, int year, int pupils, string letter = "A") =>
+        new($"y{year}{letter}", year, letter, $"classroom-{index:00}", pupils);
+
+    public static PlannerTeacher Teacher(string id, params string[] subjects) =>
+        new(id, subjects);
+
+    public static RoomNode Classroom(int index, int desks) =>
+        new()
+        {
+            Id = $"classroom-{index:00}",
+            Def = "Classroom",
+            Building = "main",
+            Floor = "floor-1",
+            Label = $"{101 + index}",
+            Seats = desks,
+        };
+
+    public static string RepoRoot()
+    {
+        var dir = new DirectoryInfo(AppContext.BaseDirectory);
+        while (dir is not null && !File.Exists(Path.Combine(dir.FullName, "h-school.sln")))
+        {
+            dir = dir.Parent;
+        }
+
+        if (dir is null)
+        {
+            throw new InvalidOperationException("Could not find h-school.sln from the test output directory.");
+        }
+
+        return dir.FullName;
+    }
+}