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/SpikeScene.cs

@@ -0,0 +1,148 @@
+using System;
+using Friflo.Engine.ECS;
+using Friflo.Engine.ECS.Systems;
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using MrGameEng.Core;
+
+namespace KniWebSpike
+{
+    // Компоненты симуляции — платформо-независимые, как в LittleSim.
+    public struct DotPosition : IComponent
+    {
+        public float X;
+        public float Y;
+    }
+
+    public struct DotVelocity : IComponent
+    {
+        public float X;
+        public float Y;
+    }
+
+    public struct DotTint : IComponent
+    {
+        public byte R;
+        public byte G;
+        public byte B;
+    }
+
+    /// <summary>
+    /// Сцена спайка: 300 «спрайтов» в Friflo EntityStore, движение в Update-фазе
+    /// (детерминированный seed, отскок от краёв), отрисовка в Draw-фазе через
+    /// KNI SpriteBatch (WebGL). Сцена и системные корни — из MrGameEng.Core.
+    /// </summary>
+    public sealed class SpikeScene : Scene
+    {
+        private readonly Func<SpriteBatch> _spriteBatch;
+        private readonly Func<Texture2D> _pixel;
+        private readonly float _width;
+        private readonly float _height;
+
+        public SpikeScene(Func<SpriteBatch> spriteBatch, Func<Texture2D> pixel, float width, float height)
+        {
+            _spriteBatch = spriteBatch;
+            _pixel = pixel;
+            _width = width;
+            _height = height;
+        }
+
+        protected override void OnLoad()
+        {
+            var random = new Random(42);
+            for (var i = 0; i < 300; i++)
+            {
+                var angle = (float)(random.NextDouble() * Math.Tau);
+                var speed = 40f + (float)random.NextDouble() * 160f;
+                Store.CreateEntity(
+                    new DotPosition
+                    {
+                        X = (float)random.NextDouble() * _width,
+                        Y = (float)random.NextDouble() * _height,
+                    },
+                    new DotVelocity
+                    {
+                        X = MathF.Cos(angle) * speed,
+                        Y = MathF.Sin(angle) * speed,
+                    },
+                    new DotTint
+                    {
+                        R = (byte)random.Next(64, 256),
+                        G = (byte)random.Next(64, 256),
+                        B = (byte)random.Next(64, 256),
+                    }
+                );
+            }
+
+            UpdateSystems.Add(new BounceSystem(_width, _height));
+            DrawSystems.Add(new DotDrawSystem(_spriteBatch, _pixel));
+        }
+
+        private sealed class BounceSystem : QuerySystem<DotPosition, DotVelocity>
+        {
+            private readonly float _width;
+            private readonly float _height;
+
+            public BounceSystem(float width, float height)
+            {
+                _width = width;
+                _height = height;
+            }
+
+            protected override void OnUpdate()
+            {
+                var delta = Tick.deltaTime;
+                var width = _width;
+                var height = _height;
+                Query.ForEachEntity(
+                    (ref DotPosition pos, ref DotVelocity vel, Entity _) =>
+                    {
+                        pos.X += vel.X * delta;
+                        pos.Y += vel.Y * delta;
+                        if (pos.X < 0f || pos.X > width)
+                        {
+                            vel.X = -vel.X;
+                            pos.X = Math.Clamp(pos.X, 0f, width);
+                        }
+
+                        if (pos.Y < 0f || pos.Y > height)
+                        {
+                            vel.Y = -vel.Y;
+                            pos.Y = Math.Clamp(pos.Y, 0f, height);
+                        }
+                    }
+                );
+            }
+        }
+
+        private sealed class DotDrawSystem : QuerySystem<DotPosition, DotTint>
+        {
+            private readonly Func<SpriteBatch> _spriteBatch;
+            private readonly Func<Texture2D> _pixel;
+
+            public DotDrawSystem(Func<SpriteBatch> spriteBatch, Func<Texture2D> pixel)
+            {
+                _spriteBatch = spriteBatch;
+                _pixel = pixel;
+            }
+
+            protected override void OnUpdate()
+            {
+                var batch = _spriteBatch();
+                var pixel = _pixel();
+                batch.Begin();
+                Query.ForEachEntity(
+                    (ref DotPosition pos, ref DotTint tint, Entity _) =>
+                    {
+                        batch.Draw(
+                            pixel,
+                            new Rectangle((int)pos.X, (int)pos.Y, 6, 6),
+                            new Color(tint.R, tint.G, tint.B)
+                        );
+                    }
+                );
+                batch.End();
+            }
+        }
+    }
+}