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/Pages/Index.razor

@@ -0,0 +1,20 @@
+@page "/"
+@page "/index.html"
+@inject IJSRuntime JsRuntime
+@using nkast.Wasm.Canvas
+
+<PageTitle>KniWebSpike</PageTitle>
+
+<div id="canvasHolder" style="
+    background: #000;
+    margin:0%;
+    position: fixed;
+    top: 0px;
+    right: 0px;
+    bottom: 0px;
+    left: 0px;
+    width:100vw;
+    height:100vh;
+">
+    <canvas id="theCanvas" style="touch-action:none;"></canvas>
+</div>

spikes/KniWeb/Pages/Index.razor.cs

@@ -0,0 +1,36 @@
+using System;
+using Microsoft.JSInterop;
+using Microsoft.Xna.Framework;
+
+namespace KniWebSpike.Pages
+{
+    public partial class Index
+    {
+        Game _game;
+
+        protected override void OnAfterRender(bool firstRender)
+        {
+            base.OnAfterRender(firstRender);
+
+            if (firstRender)
+            {
+                JsRuntime.InvokeAsync<object>("initRenderJS", DotNetObjectReference.Create(this));
+            }
+        }
+
+        [JSInvokable]
+        public void TickDotNet()
+        {
+            // init game
+            if (_game == null)
+            {
+                _game = new KniWebSpikeGame();
+                _game.Run();
+            }
+
+            // run gameloop
+            _game.Tick();
+        }
+
+    }
+}