Fix engine-wide code review findings

Collisions: init bucket heads to -1 (QueryAabb hung before the first
rebuild), reset query stamps on truncated QueryAabb (later queries
silently dropped entities), inside-origin raycasts hit at fraction 0 for
circles too, exactly-touching boxes now pair like touching circles.

Graphics: render into the letterbox viewport so the picture matches
ScreenToWorld/WorldToScreen instead of stretching; Y-sort by the
transform pivot rather than the quad center; lock-free snapshot
LayerRegistry (parallel submit read it unsynchronized); validate
InitialCapacity; warn when UseRenderer2D drops options of a later scene.

Core: scenes are explicitly single-use (re-loading threw silently
duplicated systems/entities before — now it throws), Scene.RegisterUnload
for per-scene resources, a switch requested during the reveal phase
covers again instead of hard-swapping, borderless fullscreen
(HardwareModeSwitch off), InputCapture service for input-suppressing
overlays, host disposes the transition renderer and IDisposable services
on shutdown.

Input: game input reads as released while InputCapture is held; mouse
position and wheel freeze so deltas stay zero.

DevConsole: holds InputCapture while open (typing no longer drives the
camera), Revision increments only under the lock, quoted command
arguments, history capped at 256.

UI: scene Desktop skips Myra input processing while the console is open
(clicks no longer fall through), is disposed on scene unload, and Myra
init no longer depends on a process-static flag.

Audio: validate channel count/sample rate before stopping the previous
track, empty looped oggs no longer hang FillBuffers, the instance stops
when a non-looping track drains (IsPlaying was stuck true).

Atlases: metadata v2 stores per-source size+mtime snapshots, so
timestamp-preserving copies and renames invalidate correctly; loader
checks the version and disposes pages on partial load failure; shared
pages never exceed a non-POT MaxPageSize; oversized items pack first
onto exact-size pages instead of splitting an open shared page; the CLI
validates numeric options.

Assets.Generator: file names are escaped in XML docs and string
literals, members no longer collide with the enclosing class (CS0542),
and the Assets root is resolved against build_property.projectdir so
nested "Assets" directories do not shift region paths.

Pathfinding: queries throw when the grid was resized after construction;
generation stamps survive int overflow.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/MrGameEng.Graphics/Layers.cs

@@ -23,7 +23,11 @@ public enum LayerSortMode
     /// <summary>Order by the sprite's <see cref="Sprite.Depth"/> value (smaller = drawn first).</summary>
     Depth,
 
-    /// <summary>Order by world Y position (top-down games: lower on screen = drawn in front).</summary>
+    /// <summary>
+    /// Order by the entity's world Y position (<see cref="Transform2D.Position"/>):
+    /// top-down games, lower on screen = drawn in front. Place sprite origins at the
+    /// feet/base so the sort point matches the visual anchor.
+    /// </summary>
     YSort,
 }
 
@@ -32,31 +36,51 @@ public sealed record RenderLayer(LayerId Id, string Name, LayerSpace Space, Laye
 
 /// <summary>
 /// Registry of render layers. Layers are registered up front (typically when the renderer is
-/// created) and drawn in registration order. Maximum 256 layers.
+/// created) and drawn in registration order. Maximum 256 layers. Reads are lock-free and
+/// thread-safe (the renderer reads layers from parallel submit workers); registration swaps
+/// an immutable snapshot, so registering mid-frame never tears a concurrent read.
 /// </summary>
 public sealed class LayerRegistry
 {
-    private readonly List<RenderLayer> _layers = [];
+    private readonly object _sync = new();
+    private volatile RenderLayer[] _layers = [];
 
     /// <summary>Creates a registry containing the built-in "Default" world layer.</summary>
     public LayerRegistry() => Register("Default");
 
     /// <summary>Number of registered layers.</summary>
-    public int Count => _layers.Count;
+    public int Count => _layers.Length;
 
     /// <summary>Registers a layer drawn after all previously registered ones.</summary>
     public LayerId Register(string name, LayerSpace space = LayerSpace.World, LayerSortMode sortMode = LayerSortMode.Depth)
     {
-        if (_layers.Count == 256)
+        lock (_sync)
         {
-            throw new InvalidOperationException("Maximum number of render layers (256) reached.");
-        }
+            var layers = _layers;
+            if (layers.Length == 256)
+            {
+                throw new InvalidOperationException("Maximum number of render layers (256) reached.");
+            }
 
-        var id = new LayerId((byte)_layers.Count);
-        _layers.Add(new RenderLayer(id, name, space, sortMode));
-        return id;
+            var id = new LayerId((byte)layers.Length);
+            var grown = new RenderLayer[layers.Length + 1];
+            Array.Copy(layers, grown, layers.Length);
+            grown[layers.Length] = new RenderLayer(id, name, space, sortMode);
+            _layers = grown;
+            return id;
+        }
     }
 
-    /// <summary>Returns the layer with the given id.</summary>
-    public RenderLayer this[LayerId id] => _layers[id.Value];
+    /// <summary>Returns the layer with the given id; throws when the id was never registered.</summary>
+    public RenderLayer this[LayerId id]
+    {
+        get
+        {
+            var layers = _layers;
+            return id.Value < layers.Length
+                ? layers[id.Value]
+                : throw new ArgumentOutOfRangeException(
+                    nameof(id), $"Render layer {id.Value} is not registered (registered: {layers.Length}).");
+        }
+    }
 }

src/MrGameEng.Graphics/Renderer2D.cs

@@ -67,6 +67,7 @@ public sealed class Renderer2D : IDisposable
     {
         _device = device;
         _options = options ?? new Renderer2DOptions();
+        ArgumentOutOfRangeException.ThrowIfLessThan(_options.InitialCapacity, 1, nameof(options));
         _batcher = new SpriteBatcher(_options.InitialCapacity);
         _vertices = new VertexPositionColorTexture[_options.InitialCapacity * 4];
         _vertexBuffer = new DynamicVertexBuffer(
@@ -201,7 +202,26 @@ public sealed class Renderer2D : IDisposable
         _device.SetVertexBuffer(_vertexBuffer);
         _device.Indices = _indexBuffer;
 
+        // Виртуальное разрешение рисуется в letterbox-прямоугольник — тот же, по которому
+        // считают ScreenToWorld/WorldToScreen; иначе картинка растягивается мимо маппинга.
+        var previousViewport = _device.Viewport;
+        var letterboxed = _options.VirtualResolution is not null;
+        if (letterboxed)
+        {
+            var mapping = Camera.Mapping;
+            _device.Viewport = new Viewport(
+                (int)MathF.Round(mapping.Offset.X),
+                (int)MathF.Round(mapping.Offset.Y),
+                (int)MathF.Round(Camera.VirtualWidth * mapping.Scale),
+                (int)MathF.Round(Camera.VirtualHeight * mapping.Scale));
+        }
+
         DrawBatches(order, count);
+        if (letterboxed)
+        {
+            _device.Viewport = previousViewport;
+        }
+
         DrawMs = ToMs(Stopwatch.GetTimestamp() - uploadEnd);
     }
 
@@ -276,7 +296,9 @@ public sealed class Renderer2D : IDisposable
             return SubmitResult.Culled;
         }
 
-        var depth = layer.SortMode == LayerSortMode.YSort ? center.Y : sprite.Depth;
+        // Y-sort по пивоту (Transform2D.Position), а не по центру квада: спрайты разной
+        // высоты с origin «в ногах» сортируются по ногам, как принято в top-down.
+        var depth = layer.SortMode == LayerSortMode.YSort ? transform.Position.Y : sprite.Depth;
 
         instance = new SpriteInstance
         {

src/MrGameEng.Graphics/SceneGraphicsExtensions.cs

@@ -22,6 +22,12 @@ public static class SceneGraphicsExtensions
             renderer = new Renderer2D(scene.Context.GraphicsDevice, options);
             services.Add(renderer);
         }
+        else if (options is not null)
+        {
+            Log.Warning(
+                "UseRenderer2D: the renderer already exists, the passed options are ignored " +
+                "(Renderer2D is a shared service configured by its first user).");
+        }
 
         scene.DrawSystems.Add(new CameraSystem(renderer));
         scene.DrawSystems.Add(new SpriteRenderSystem(renderer));