docs: add PR description in Chinese and English

PULL_REQUEST_EN.md

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+# fix(export): "Date Range" file naming mode not working in export global config
+
+## Problem
+
+In the **Export page → Global Settings → Export File Naming Mode**, selecting "Date Range Mode" (`date-range`) has no effect. The exported files always use the "Classic Mode" (`classic`) naming format without any date range information. The option is completely ignored.
+
+## Root Cause
+
+The `fileNamingMode` config value is lost at 4 breakpoints along the data flow from saving (`ExportDefaultsSettingsForm` → `configService.setExportDefaultFileNamingMode()`) to actual usage (Electron side `ExportOrchestrator` → `normalizeFileNamingMode()`):
+
+### 1. `types.ts` — `ExportOptions` interface missing `fileNamingMode` field
+
+The frontend type definition lacks this property, so TypeScript cannot track its existence. The data is already lost at the very first step of data flow.
+
+### 2. `constants.ts` — `createDefaultExportOptions()` missing default value
+
+No default value is set when creating export options, leaving `fileNamingMode` as `undefined`.
+
+### 3. `useExportConfig.ts` — Not loaded on init, not persisted in `updateOptions`
+
+- Initial load does not call `getExportDefaultFileNamingMode()`
+- Changes via `updateOptions` are not persisted to storage via `setExportDefaultFileNamingMode()`
+
+### 4. `ExportPage.tsx` — `handleExportDefaultsChanged` drops the `fileNamingMode` patch
+
+The callback fired when closing the global settings modal only passes `format` and `avatars` to `updateOptions`, completely ignoring `fileNamingMode`.
+
+## Fix
+
+Bridged each gap in the data flow so the config value flows end-to-end: save → load → propagate → use.
+
+## Changes
+
+| File | Change Type | Description |
+|------|-------------|-------------|
+| `src/pages/Export/types.ts` | New field | Added `fileNamingMode: 'classic' \| 'date-range'` to `ExportOptions` interface |
+| `src/pages/Export/constants.ts` | New default | Added `fileNamingMode: 'classic'` default in `createDefaultExportOptions()` |
+| `src/pages/Export/hooks/useExportConfig.ts` | Load + persist | Added `getExportDefaultFileNamingMode()` to initial `Promise.all`; assign loaded value to `newOptions.fileNamingMode`; added `setExportDefaultFileNamingMode()` persistence in `updateOptions` |
+| `src/pages/Export/ExportPage.tsx` | Propagate + fix key | Propagate `fileNamingMode` in `handleExportDefaultsChanged`; fixed incorrect key name `defaultFormat` → `format` |
+
+## Verification
+
+- Tested on Windows desktop client: selecting "Date Range Mode" produces correct filenames with date range tokens (e.g. `Private_ZhangSan_20250101-20250331.json`)
+- TypeScript type check passes, build succeeds with no errors

PULL_REQUEST_ZH.md

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+# 修复：导出文件命名方式中"时间范围模式"选项不生效
+
+## 问题描述
+
+在导出页面的**全局配置 → 导出文件命名方式**中，选择"时间范围模式"（date-range）后，实际导出的文件名仍然使用"简洁模式"（classic），不包含时间范围信息。该选项完全不生效。
+
+## 根因分析
+
+`fileNamingMode` 配置在保存（`ExportDefaultsSettingsForm` → `configService.setExportDefaultFileNamingMode()`）到实际使用（Electron 端 `ExportOrchestrator` → `normalizeFileNamingMode()`）之间的数据流中存在 4 处断裂：
+
+### 1. `types.ts` — `ExportOptions` 接口缺少 `fileNamingMode` 字段
+
+前端类型定义中没有该属性，导致 TypeScript 类型系统无法感知这个选项的存在，数据传递的第一步就已丢失。
+
+### 2. `constants.ts` — `createDefaultExportOptions()` 缺少默认值
+
+创建默认选项时未设置 `fileNamingMode`，值始终为 `undefined`。
+
+### 3. `useExportConfig.ts` — 初始加载未读取、`updateOptions` 未持久化
+
+- 从 config 初始化时未调用 `getExportDefaultFileNamingMode()`
+- 在 `updateOptions` 中修改时未调用 `setExportDefaultFileNamingMode()` 持久化到存储
+
+### 4. `ExportPage.tsx` — `handleExportDefaultsChanged` 丢弃了 `fileNamingMode` patch
+
+全局配置弹窗关闭时触发的回调中，只传递了 `format` 和 `avatars` 给 `updateOptions`，`fileNamingMode` 被完全忽略。
+
+## 修复方案
+
+逐层打通数据流，使配置从保存 → 加载 → 传递 → 使用形成完整闭环。
+
+## 变更列表
+
+| 文件 | 改动类型 | 说明 |
+|------|---------|------|
+| `src/pages/Export/types.ts` | 新增字段 | 在 `ExportOptions` 接口中新增 `fileNamingMode: 'classic' \| 'date-range'` |
+| `src/pages/Export/constants.ts` | 新增默认值 | 在 `createDefaultExportOptions()` 中新增 `fileNamingMode: 'classic'` 默认值 |
+| `src/pages/Export/hooks/useExportConfig.ts` | 新增加载+持久化 | `Promise.all` 中添加 `getExportDefaultFileNamingMode()`；加载后赋值给 `newOptions.fileNamingMode`；`updateOptions` 中添加 `setExportDefaultFileNamingMode()` 持久化 |
+| `src/pages/Export/ExportPage.tsx` | 补充传递 + 修复 key | `handleExportDefaultsChanged` 中添加 `fileNamingMode` 传递；同时修复了 `format` key 名错误（`defaultFormat` → `format`） |
+
+## 验证
+
+- 在 Windows 桌面客户端上测试通过：选择"时间范围模式"后导出，文件名正确包含日期范围（示例：`私聊_张三_20250101-20250331.json`）
+- TypeScript 类型检查通过，编译无错误