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.Core/SceneManager.cs

@@ -36,18 +36,24 @@ public sealed class SceneManager
     /// Requests a switch to <paramref name="scene"/>. Without a transition the swap happens at
     /// the start of the next update tick; with one, the old scene is first covered.
     /// Passing null unloads the current scene. Calling during an active transition replaces
-    /// the pending target scene.
+    /// the pending target scene; a switch requested while a transition is revealing starts
+    /// covering again from the current coverage.
     /// </summary>
     public void Switch(Scene? scene, Transition? transition = null)
     {
         _pending = scene;
         _hasPending = true;
 
-        if (_state == State.Idle && transition is not null)
+        if (transition is not null && _state != State.CoveringOut)
         {
             _transition = transition;
+            if (_state == State.Idle)
+            {
+                _coverage = 0f;
+            }
+
+            // Из RevealingIn закрытие продолжается с текущего coverage — без скачка.
             _state = State.CoveringOut;
-            _coverage = 0f;
         }
     }
 
@@ -99,6 +105,13 @@ public sealed class SceneManager
         _transition!.Draw(_renderer, Math.Clamp(_coverage, 0f, 1f), phase);
     }
 
+    /// <summary>Disposes the lazily created transition renderer. Called on host shutdown.</summary>
+    internal void DisposeRenderer()
+    {
+        _renderer?.Dispose();
+        _renderer = null;
+    }
+
     internal void ApplyPending()
     {
         if (!_hasPending)