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

vite.config.ts

@@ -36,4 +36,20 @@ export default defineConfig({
       },
     },
   },
+  test: {
+    globals: true,
+    environment: 'jsdom',
+    setupFiles: './src/tests/setup.ts',
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'json', 'html'],
+      exclude: [
+        'node_modules/',
+        'src/tests/',
+        '*.config.ts',
+        '**/*.d.ts',
+        'dist/',
+      ],
+    },
+  },
 });