feat: 完善多账号连接诊断与聊天媒体导出

- 新增微信账号发现、环境诊断和分步数据库连接引导
- 支持按账号安全保存数据库密钥及快速切换账号
- 完善 WCDB 历史消息分片读取和分页状态提示
- 支持导出图片、视频和语音，提供原图优先及缩略图回退
- 更新安装指引、兼容版本说明和相关自动化测试

src/shared/connection-diagnostics.ts

@@ -0,0 +1,16 @@
+import type { DatabaseKeyEnvironment } from './database-key'
+
+export function buildSafeDiagnosticSummary(
+  environment: Omit<DatabaseKeyEnvironment, 'diagnosticSummary'>
+): string {
+  return [
+    `WechatExplorer: ${environment.appVersion}`,
+    `操作系统: ${environment.osVersion}`,
+    `微信客户端: ${environment.wechatVersion}`,
+    `数据结构: ${environment.dataStructureVersion}`,
+    `数据目录: ${environment.dataDirectoryDetected ? '已检测到' : '未检测到'}`,
+    `微信进程: ${environment.wechatRunning ? '运行中' : '未运行'}`,
+    `数据库连接: ${environment.dbConnected ? '已连接' : '未连接'}`,
+    `安全存储: ${environment.encryptionAvailable ? '可用' : '不可用'}`
+  ].join('\n')
+}

src/shared/database-key.ts

@@ -24,8 +24,36 @@ export interface DatabaseKeyStorageResult {
   encryptionAvailable: boolean
 }
 
+export type AccountLoginStatus = 'current' | 'other' | 'unknown'
+
+export interface WechatAccountCandidate {
+  id: string
+  accountRoot: string
+  directoryName: string
+  wxid?: string
+  nickname?: string
+  avatar?: string
+  hasSavedDbKey: boolean
+  loginStatus: AccountLoginStatus
+  selectedByInput: boolean
+}
+
+export interface AccountDiscoveryResult {
+  success: boolean
+  inputKind?: 'root' | 'account'
+  accounts: WechatAccountCandidate[]
+  preselectedAccountId?: string
+  error?: string
+}
+
 export interface DatabaseKeyEnvironment {
   platform: NodeJS.Platform
+  osVersion: string
+  appVersion: string
+  wechatVersion: string
+  dataStructureVersion: string
+  dataDirectoryDetected: boolean
+  diagnosticSummary: string
   autoDetectSupported: boolean
   wechatRunning: boolean
   accountIdentified: boolean

src/shared/export-media.ts

@@ -0,0 +1,22 @@
+import type { ExportRequest } from './export'
+
+export type ImageExportAttempt = {
+  allowThumbnail: boolean
+  preferThumbnail: boolean
+  fallback: boolean
+}
+
+export function getImageExportAttempts(
+  request: Pick<ExportRequest, 'preferOriginal' | 'fallbackThumbnail'>
+): ImageExportAttempt[] {
+  if (request.preferOriginal === false) {
+    return [{ allowThumbnail: true, preferThumbnail: true, fallback: false }]
+  }
+  const attempts: ImageExportAttempt[] = [
+    { allowThumbnail: false, preferThumbnail: false, fallback: false }
+  ]
+  if (request.fallbackThumbnail !== false) {
+    attempts.push({ allowThumbnail: true, preferThumbnail: true, fallback: true })
+  }
+  return attempts
+}

src/shared/export.ts

@@ -23,6 +23,9 @@ export interface ExportRequest {
   endTime?: number
   kinds: ExportMessageKind[]
   includeMedia: boolean
+  preferOriginal?: boolean
+  fallbackThumbnail?: boolean
+  keepMissing?: boolean
   includeAvatars?: boolean
   avatarUrls?: Record<string, string>
   nameMode?: ExportNameMode