Add MrGameEng.Atlases: texture atlas builder, runtime loader and CLI tool

AtlasBuilder packs a directory tree of loose images into atlas pages plus
JSON metadata (deterministic shelf packing, incremental rebuilds, orphan
cleanup); TextureAtlas loads them back handing out Texture2DRegions, so
sprites from one page batch into a single draw call. The asset handle
generator maps .atlas files to TextureAtlas and skips page images.
Demonstrated in the sample (Assets/Atlases + 'atlas' console command),
wrapped as tools/MrGameEng.AtlasTool for build scripts.

Documented dependency exception: Atlases depends on Graphics and Assets.

samples/MrGameEng.Sample/Scenes/MainScene.cs

@@ -1,6 +1,7 @@
 using Friflo.Engine.ECS;
 using Microsoft.Xna.Framework;
 using MrGameEng.Assets;
+using MrGameEng.Atlases;
 using MrGameEng.Audio;
 using MrGameEng.Core;
 using MrGameEng.DevConsole;
@@ -36,6 +37,11 @@ public sealed class MainScene : Scene
         var shapesTexture = assets.Load(GameAssets.Textures.Shapes);
         var beep = assets.Load(GameAssets.Sounds.Beep);
 
+        // Текстурный атлас: Assets/Atlases собран утилитой MrGameEng.AtlasTool из Assets/Textures
+        // (см. README). Регионы адресуются исходным путём без расширения и батчатся в один draw call.
+        Context.UseTextureAtlases();
+        var atlas = assets.Load(GameAssets.Atlases.Textures);
+
         var shapeRegions = new[]
         {
             new Texture2DRegion(shapesTexture, new Rectangle(0, 0, 32, 32)),
@@ -87,6 +93,15 @@ public sealed class MainScene : Scene
             playerSprite,
             new SpriteAnimator(blink));
 
+        // Пара спрайтов из атласа рядом со стартом игрока — вся пара рисуется одним draw call.
+        var atlasShowcase = new[] { ("player", -80f), ("shapes", 80f) };
+        foreach (var (key, offsetX) in atlasShowcase)
+        {
+            var sprite = new Sprite(atlas.GetRegion(key), SampleLayers.Actors);
+            sprite.CenterOrigin();
+            Store.CreateEntity(new Transform2D(new Vector2(offsetX, -120f)), sprite);
+        }
+
         var camera = Store.CreateEntity(new Camera(Vector2.Zero, zoom: 1f, bounds: WorldBounds));
 
         // HUD: золотой квадрат в углу на screen-space слое — не двигается с камерой.
@@ -131,6 +146,14 @@ public sealed class MainScene : Scene
             }
         });
         console.Register("beep", "play the beep sound", (_, _) => audio.Play(beep));
+        console.Register("atlas", "list texture atlas regions", (c, _) =>
+        {
+            c.WriteLine($"atlas '{atlas.Name}': {atlas.Pages.Count} page(s), {atlas.Regions.Count} region(s)");
+            foreach (var (key, region) in atlas.Regions.OrderBy(r => r.Key, StringComparer.Ordinal))
+            {
+                c.WriteLine($"  {key}: {region.Bounds.Width}x{region.Bounds.Height} at ({region.Bounds.X},{region.Bounds.Y})");
+            }
+        });
 
         UpdateSystems.Add(new PlayerControlSystem(player, actions, audio, beep, console));
         UpdateSystems.Add(new BounceSystem(WorldBounds));