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/App.razor

@@ -0,0 +1,12 @@
+<Router AppAssembly="@typeof(App).Assembly">
+    <Found Context="routeData">
+        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
+        <FocusOnNavigate RouteData="@routeData" Selector="h1" />
+    </Found>
+    <NotFound>
+        <PageTitle>Not found</PageTitle>
+        <LayoutView Layout="@typeof(MainLayout)">
+            <p role="alert">Sorry, there's nothing at this address.</p>
+        </LayoutView>
+    </NotFound>
+</Router>