KNI spike: engine core + Friflo render via WebGL in the browser

spikes/KniWeb (outside LittleSim.sln): a kni-blazor-gl template project
(KNI 4.2.9001, net8.0) referencing MrGameEng.Core directly. A mini-host
in the GameHost mold drives EngineContext/GameClock/Scene phases over
KNI's Game; the scene moves 300 Friflo entities in the update phase and
draws them with SpriteBatch (WebGL). Verified in a real browser: sprites
render and animate, browser console is clean.

Decision (docs/web-client.md): path A — KNI — is the primary route for
the web client; the core runs in Blazor WASM unchanged thanks to the
Core/Host split. Known follow-ups: per-platform compilation of the
graphics libraries against nkast.* packages, shader compatibility for
Renderer2D, HTTP-served content instead of the filesystem.

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

spikes/KniWeb/KniWebSpikeGame.cs

@@ -0,0 +1,58 @@
+using System;
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using Microsoft.Xna.Framework.Input;
+using MrGameEng.Core;
+
+namespace KniWebSpike
+{
+    /// <summary>
+    /// Мини-хост в духе MrGameEng.Host.GameHost, но поверх KNI (BlazorGL/WebGL):
+    /// владеет EngineContext ядра, гонит GameClock и фазы сцены. Если этот класс
+    /// работает в браузере — будущий MrGameEng.Host.Web реализуем.
+    /// </summary>
+    public class KniWebSpikeGame : Game
+    {
+        public EngineContext Context { get; } = new EngineContext();
+
+        private GraphicsDeviceManager _graphics;
+        private SpriteBatch _spriteBatch;
+        private Texture2D _pixel;
+
+        public KniWebSpikeGame()
+        {
+            _graphics = new GraphicsDeviceManager(this);
+            Content.RootDirectory = "Content";
+        }
+
+        protected override void Initialize()
+        {
+            base.Initialize();
+            var viewport = GraphicsDevice.Viewport;
+            Context.Scenes.Switch(
+                new SpikeScene(() => _spriteBatch, () => _pixel, viewport.Width, viewport.Height)
+            );
+        }
+
+        protected override void LoadContent()
+        {
+            _spriteBatch = new SpriteBatch(GraphicsDevice);
+            _pixel = new Texture2D(GraphicsDevice, 1, 1);
+            _pixel.SetData(new[] { Color.White });
+        }
+
+        protected override void Update(GameTime gameTime)
+        {
+            Context.Clock.Advance((float)gameTime.ElapsedGameTime.TotalSeconds);
+            Context.Scenes.Update(Context.Clock);
+            base.Update(gameTime);
+        }
+
+        protected override void Draw(GameTime gameTime)
+        {
+            GraphicsDevice.Clear(new Color(12, 16, 24));
+            Context.Scenes.Draw(Context.Clock);
+            base.Draw(gameTime);
+        }
+    }
+}