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>

playwright.config.js

@@ -0,0 +1,32 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './tests/e2e',
+  fullyParallel: true,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 2 : 0,
+  workers: process.env.CI ? 1 : undefined,
+  reporter: 'html',
+  use: {
+    baseURL: 'http://localhost:5173',
+    trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
+  },
+
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+    {
+      name: 'mobile',
+      use: { ...devices['iPhone 12'] },
+    },
+  ],
+
+  webServer: {
+    command: 'npm run dev',
+    url: 'http://localhost:5173',
+    reuseExistingServer: !process.env.CI,
+  },
+});