Add comprehensive test suite with Vitest and Playwright

**Unit Tests (Vitest):**
- Test game logic: inventory management, barrel calculations
- Test whale hunting mechanics: fuel consumption, oil rewards, health system
- Test mobile detection patterns
- Test crosshair bounds and scene transitions
- 21 unit tests covering core game logic
- Fast execution with jsdom environment

**E2E Tests (Playwright):**
- Test complete game flows from intro to hunting
- Test scene navigation and transitions
- Test whale hunting interaction
- Test mobile compatibility and touch interactions
- Test desktop scaling on various viewports
- Run on both desktop (Chrome) and mobile (iPhone 12) configurations

**Test Scripts:**
- npm test - Run unit tests
- npm run test:ui - Run unit tests with UI
- npm run test:coverage - Run with coverage report
- npm run test:e2e - Run E2E tests
- npm run test:e2e:ui - Run E2E tests with UI
- npm run test:all - Run all tests

**Configuration:**
- Vitest configured with jsdom for fast unit testing
- Playwright configured with automatic dev server startup
- Test coverage reporting enabled
- Separate unit and E2E test directories

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

package.json

@@ -6,15 +6,30 @@
   "scripts": {
     "dev": "vite",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest",
+    "test:ui": "vitest --ui",
+    "test:coverage": "vitest --coverage",
+    "test:e2e": "playwright test",
+    "test:e2e:ui": "playwright test --ui",
+    "test:all": "npm run test && npm run test:e2e"
   },
-  "keywords": ["game", "phaser", "adventure", "point-and-click"],
+  "keywords": [
+    "game",
+    "phaser",
+    "adventure",
+    "point-and-click"
+  ],
   "author": "",
   "license": "MIT",
   "dependencies": {
     "phaser": "^3.80.1"
   },
   "devDependencies": {
-    "vite": "^5.0.0"
+    "@playwright/test": "^1.57.0",
+    "@vitest/ui": "^4.0.16",
+    "jsdom": "^27.3.0",
+    "vite": "^5.0.0",
+    "vitest": "^4.0.16"
   }
 }