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.Audio/MusicPlayer.cs

@@ -40,9 +40,25 @@ public sealed class MusicPlayer : IDisposable
     /// <summary>Starts streaming <paramref name="track"/>, stopping the previous one.</summary>
     public void Play(MusicTrack track, bool loop = true)
     {
+        // Валидация до Stop(): негодный файл не должен обрывать играющий трек.
+        var reader = new VorbisReader(track.FullPath);
+        if (reader.Channels is < 1 or > 2)
+        {
+            reader.Dispose();
+            throw new NotSupportedException(
+                $"Music '{track.FullPath}' has {reader.Channels} channels; only mono and stereo are supported.");
+        }
+
+        if (reader.SampleRate is < 8000 or > 48000)
+        {
+            reader.Dispose();
+            throw new NotSupportedException(
+                $"Music '{track.FullPath}' has sample rate {reader.SampleRate} Hz; supported range is 8000–48000 Hz.");
+        }
+
         Stop();
         _loop = loop;
-        _reader = new VorbisReader(track.FullPath);
+        _reader = reader;
 
         // ~0.5 seconds of samples per submitted buffer.
         var samplesPerBuffer = _reader.SampleRate * _reader.Channels / 2;
@@ -91,13 +107,22 @@ public sealed class MusicPlayer : IDisposable
             var read = _reader.ReadSamples(_sampleBuffer, 0, _sampleBuffer.Length);
             if (read == 0)
             {
-                if (!_loop)
+                // SamplePosition > 0 отличает конец трека от пустого файла: после перемотки
+                // на 0 повторный read == 0 не зацикливается, а завершает воспроизведение.
+                if (_loop && _reader.SamplePosition > 0)
                 {
-                    return;
+                    _reader.SamplePosition = 0;
+                    continue;
                 }
 
-                _reader.SamplePosition = 0;
-                continue;
+                // Конец незацикленного трека (или пустой файл): когда буферы доиграли,
+                // останавливаем инстанс — иначе IsPlaying остаётся true навсегда.
+                if (_instance.PendingBufferCount == 0)
+                {
+                    _instance.Stop();
+                }
+
+                return;
             }
 
             for (var i = 0; i < read; i++)