Add in-game developer console (MrGameEng.DevConsole)

Core gains a static Log (Debug/Info/Warning/Error + event); the engine
logs key events like scene switches. The console captures Log output
into a 2048-line ring buffer and executes registered commands with
input history (up/down), Tab prefix completion and scrolling
(PageUp/PageDown/End/wheel). Built-ins: help, clear, echo, timescale,
close, quit; games register their own (sample: stress/main/beep).

Console core is pure logic covered by headless tests; the Myra overlay
renders a single label rebuilt only when the Revision counter moves -
an idle or closed console costs nothing per frame. Toggled with the
backquote key; sample gameplay hotkeys are suppressed while open.

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

samples/MrGameEng.Sample/SampleSystems.cs

@@ -12,10 +12,16 @@ namespace MrGameEng.Sample;
 
 /// <summary>Управление игроком (WASD/стрелки) и прыжок-писк на пробел.</summary>
 public sealed class PlayerControlSystem(
-    Entity player, ActionMap<SampleAction> actions, AudioManager audio, SoundEffect beep) : BaseSystem
+    Entity player, ActionMap<SampleAction> actions, AudioManager audio, SoundEffect beep,
+    MrGameEng.DevConsole.DevConsole console) : BaseSystem
 {
     protected override void OnUpdateGroup()
     {
+        if (console.IsOpen)
+        {
+            return;
+        }
+
         ref var transform = ref player.GetComponent<Transform2D>();
         var move = new Vector2(
             actions.GetAxis(SampleAction.MoveLeft, SampleAction.MoveRight),
@@ -131,6 +137,11 @@ public sealed class SceneHotkeysSystem(
 {
     protected override void OnUpdateGroup()
     {
+        if (context.Services.Get<MrGameEng.DevConsole.DevConsole>().IsOpen)
+        {
+            return;
+        }
+
         if (actions.IsPressed(SampleAction.Pause))
         {
             context.Clock.TimeScale = context.Clock.TimeScale > 0f ? 0f : 1f;