feat(test): add comprehensive test suite and testing infrastructure

- Add vitest configuration with coverage reporting
- Create test setup file with DOM mocks
- Add tests for state management, helpers, and tool configurations
- Update tsconfig and package.json for testing support
- Clean up unused comments and improve code style

vitest.config.ts

@@ -0,0 +1,55 @@
+import { defineConfig } from 'vitest/config';
+import { resolve } from 'path';
+
+export default defineConfig({
+  test: {
+    // Enable global test APIs (describe, it, expect, etc.)
+    globals: true,
+    
+    // Simulate browser environment
+    environment: 'jsdom',
+    
+    // Setup files to run before tests
+    setupFiles: ['./src/tests/setup.ts'],
+    
+    // Coverage configuration
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'json', 'html', 'lcov'],
+      reportsDirectory: './coverage',
+      exclude: [
+        'node_modules/',
+        'src/tests/',
+        'dist/',
+        '*.config.ts',
+        '*.config.js',
+        '**/*.d.ts',
+        'public/',
+        'scripts/',
+      ],
+      // Set thresholds (optional)
+      thresholds: {
+        lines: 80,
+        functions: 80,
+        branches: 80,
+        statements: 80,
+      },
+    },
+    
+    // Include/exclude patterns
+    include: ['src/**/*.{test,spec}.{js,ts}'],
+    exclude: ['node_modules', 'dist', '.idea', '.git', '.cache'],
+    
+    // Test timeout
+    testTimeout: 10000,
+    
+    // Watch options
+    watch: false,
+  },
+  
+  resolve: {
+    alias: {
+      '@': resolve(__dirname, './src'),
+    },
+  },
+});