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>

tests/MrGameEng.Core.Tests/SceneManagerTests.cs

@@ -84,4 +84,69 @@ public class SceneManagerTests
 
         Assert.Null(context.Scenes.Current);
     }
+
+    private sealed class CallbackScene(Action<Scene> onLoad) : Scene
+    {
+        protected override void OnLoad() => onLoad(this);
+    }
+
+    [Fact]
+    public void Switch_BackToLoadedSceneInstance_Throws()
+    {
+        var context = new EngineContext();
+        var first = new TrackingScene();
+        var second = new TrackingScene();
+
+        context.Scenes.Switch(first);
+        context.Scenes.Update(context.Clock);
+        context.Scenes.Switch(second);
+        context.Scenes.Update(context.Clock);
+
+        // Повторная загрузка молча задвоила бы системы и сущности — должен быть отказ.
+        context.Scenes.Switch(first);
+        Assert.Throws<InvalidOperationException>(() => context.Scenes.Update(context.Clock));
+    }
+
+    [Fact]
+    public void RegisterUnload_RunsOnUnload_InReverseOrder()
+    {
+        var context = new EngineContext();
+        var order = new List<int>();
+        var scene = new CallbackScene(s =>
+        {
+            s.RegisterUnload(() => order.Add(1));
+            s.RegisterUnload(() => order.Add(2));
+        });
+
+        context.Scenes.Switch(scene);
+        context.Scenes.Update(context.Clock);
+        Assert.Empty(order);
+
+        context.Scenes.Switch(null);
+        context.Scenes.Update(context.Clock);
+        Assert.Equal([2, 1], order);
+    }
+
+    private sealed class DisposableService : IDisposable
+    {
+        public int DisposeCount;
+
+        public void Dispose() => DisposeCount++;
+    }
+
+    [Fact]
+    public void DisposeServices_DisposesEachServiceOnce_AndSkipsExcept()
+    {
+        var registry = new ServiceRegistry();
+        var service = new DisposableService();
+        var host = new DisposableService();
+        registry.Add(service);
+        registry.Add<IDisposable>(host); // host зарегистрирован, но его освобождает вызывающий
+
+        registry.DisposeServices(except: host);
+
+        Assert.Equal(1, service.DisposeCount);
+        Assert.Equal(0, host.DisposeCount);
+        Assert.Null(registry.GetOrDefault<DisposableService>());
+    }
 }