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>

vitest.config.js

@@ -0,0 +1,20 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'jsdom',
+    include: ['tests/unit/**/*.test.js'],
+    exclude: ['tests/e2e/**'],
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'html', 'lcov'],
+      exclude: [
+        'node_modules/',
+        'dist/',
+        '*.config.js',
+        'tests/e2e/**'
+      ]
+    }
+  }
+});