fix: E2E mock 统一 + CSV 引号字段解析

E2E:
- createIpcMock 支持 overrides 参数，保持 default: throw 行为
- search-clean.spec.ts 删除 30 行内联 mock，改用 createIpcMock(overrides)

Rust:
- 新增 parse_csv_line: 支持引号包裹字段 + 双引号转义 (RFC 4180 子集)
- import_csv 改用 parse_csv_line 替代 split(',')
- 与 TS 端 parseCsvLine 逻辑对称

测试: Rust 48 → 52 (+4), Frontend 100

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

e2e/tests/search-clean.spec.ts

@@ -1,28 +1,12 @@
 import { test, expect } from '@playwright/test';
+import { createIpcMock } from '../mocks/ipc';
 
 test.beforeEach(async ({ page }) => {
-  await page.addInitScript(() => {
-    window.__TAURI_INTERNALS__ = {
-      invoke: async (cmd, _args) => {
-        switch (cmd) {
-          case 'check_admin': return true;
-          case 'load_system_paths': return ['C:\\\\Windows', 'invalid_path', 'C:\\\\Temp'];
-          case 'load_user_paths': return [];
-          case 'load_disabled_state': return { system: [], user: [] };
-          case 'save_system_paths': return undefined;
-          case 'save_user_paths': return undefined;
-          case 'save_disabled_state': return undefined;
-          case 'backup_registry': return '';
-          case 'broadcast_env_change': return undefined;
-          case 'validate_path': return false;
-          case 'expand_env_vars': return '';
-          case 'read_text_file': return '';
-          case 'get_appdata_dir': return '';
-          default: return undefined;
-        }
-      }
-    };
-  });
+  await page.addInitScript(createIpcMock({
+    load_system_paths: ['C:\\Windows', 'invalid_path', 'C:\\Temp'],
+    load_user_paths: [],
+    validate_path: false,
+  }));
   await page.goto('/');
 });