✨ add ZoomTestScene with Phaser default zoom for analysis

Separate test environment at /test.html (own Vite entry, own Phaser
instance). ZoomTestScene renders a 50×50 tile grid with crosshair
markers and a live HUD overlay showing zoom, scroll, viewport in px
and tiles, mouse world/screen/tile coords, and renderer info.
Zoom uses plain cam.setZoom() — no mouse tracking — to observe
Phaser's default center-anchor behavior.

src/test/main.ts

@@ -0,0 +1,21 @@
+import Phaser from 'phaser'
+import { ZoomTestScene } from './ZoomTestScene'
+
+const config: Phaser.Types.Core.GameConfig = {
+  type: Phaser.AUTO,
+  width: window.innerWidth,
+  height: window.innerHeight,
+  backgroundColor: '#0d1a0d',
+  scene: [ZoomTestScene],
+  scale: {
+    mode: Phaser.Scale.RESIZE,
+    autoCenter: Phaser.Scale.CENTER_BOTH,
+  },
+  render: {
+    pixelArt: false,
+    antialias: true,
+    roundPixels: true,
+  },
+}
+
+new Phaser.Game(config)