✨ 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.

vite.config.ts

@@ -1,4 +1,5 @@
 import { defineConfig } from 'vite'
+import { resolve } from 'path'
 
 export default defineConfig({
   server: {
@@ -7,6 +8,12 @@ export default defineConfig({
   },
   build: {
     outDir: 'dist',
-    assetsInlineLimit: 0
-  }
+    assetsInlineLimit: 0,
+    rollupOptions: {
+      input: {
+        main: resolve(__dirname, 'index.html'),
+        test: resolve(__dirname, 'test.html'),
+      },
+    },
+  },
 })