feat(i18n): add English support for host-side chat messages

Wrap all user-facing chat text in src/channels with a host-side t()
translator (Chinese is the identity default, so untranslated text is
always sent verbatim in Chinese). English is selected via the host
plugin config `language: en` or the DSH_IM_LANGUAGE environment
variable, and the settings UI keeps following the DSH web locale.

- add src/channels/shared/i18n.mjs with setImHostLanguage/t() and a
  Chinese-key -> English dictionary split by area (shared + channels)
- complete the English dictionary for every t() key in src/channels,
  including the feishu channel (welcome/help, repair flow, interactive
  cards, watch flow) and the shared command/approval/stream text
- wrap previously untranslated chat-facing strings in feishu bridge,
  feishu runtime, editable-message-stream, harness-client,
  connection-test and image-prompt
- dedupe dictionary entries that existed in multiple channel files and
  canonicalize conflicting translations into the shared dictionaries
- extend the i18n unit test to decode string-literal escapes so keys
  containing \n are checked correctly
- document the language switch in README.md, README.en.md and
  CHANGELOG.md, and rebuild lib/index.js

Added English support for bot chat messages across all nine IM
channels and AI Office without changing any Chinese output.

src/channels/shared/i18n-en/shared-a.mjs

@@ -0,0 +1,78 @@
+// English translations (shared-a area). Keys are exact Chinese literals passed to t().
+export default {
+  '这个问题已在其他客户端处理，无需再次回答。':
+    'This question has already been answered from another client; no further reply is needed.',
+  '任务已完成。': 'Task completed.',
+  '结果文件': 'result file',
+  '结果文件「{name}」的发送结果未能确认，请先检查聊天内是否已收到，不要立即重试。':
+    'The delivery result of the result file "{name}" could not be confirmed. Please check whether it already arrived in the chat before retrying.',
+  '结果文件「{name}」已生成，但 Slack 应用缺少 files:write 权限。请更新 Manifest、重新安装应用并重新连接机器人后重试。':
+    'The result file "{name}" was generated, but the Slack app is missing the files:write permission. Please update the Manifest, reinstall the app, reconnect the bot, and try again.',
+  '结果文件「{name}」已生成，但机器人缺少 Discord 的 Send Messages、Attach Files 或 Read Message History 权限。':
+    'The result file "{name}" was generated, but the bot is missing the Discord Send Messages, Attach Files, or Read Message History permission.',
+  '结果文件「{name}」已生成，但 Telegram 不允许机器人在当前聊天发送文档，请检查聊天权限。':
+    'The result file "{name}" was generated, but Telegram does not allow the bot to send documents in this chat. Please check the chat permissions.',
+  '结果文件「{name}」已生成，但当前机器人没有文件发送权限，请检查渠道权限。':
+    'The result file "{name}" was generated, but the bot does not have permission to send files. Please check the channel permissions.',
+  '结果文件「{name}」超过当前渠道大小上限，未发送。':
+    'The result file "{name}" exceeds the size limit of this channel and was not sent.',
+  '结果文件「{name}」为空，未发送。':
+    'The result file "{name}" is empty and was not sent.',
+  '结果文件「{name}」暂时无法读取或准备发送，请确认文件仍可访问后重试。':
+    'The result file "{name}" cannot be read or prepared for sending right now. Please make sure the file is still accessible and try again.',
+  '结果文件「{name}」暂时被当前渠道限流，未能发送，请稍后重试。':
+    'The result file "{name}" was temporarily rate-limited by this channel and could not be sent. Please try again later.',
+  '结果文件「{name}」已生成，但当前渠道拒绝了该文件或文件消息。':
+    'The result file "{name}" was generated, but this channel rejected the file or file message.',
+  '结果文件「{name}」已生成，但当前渠道暂时未能发送，请稍后重试。':
+    'The result file "{name}" was generated, but this channel could not send it right now. Please try again later.',
+  '消息处理失败，请稍后重试。': 'Failed to process the message. Please try again later.',
+  '{label}机器人': '{label} bot',
+  '目前支持文字和图片消息。': 'Only text and image messages are supported at the moment.',
+  '目前支持文字、图片和文件消息。':
+    'Only text, image, and file messages are supported at the moment.',
+  '目前支持文字、图片、文件和语音转写消息。':
+    'Only text, image, file, and voice-transcription messages are supported at the moment.',
+  '目前支持文字、图片、文件，以及微信已转成文字的语音消息。':
+    'Only text, image, file, and voice messages already transcribed to text by WeChat are supported at the moment.',
+  '直接发送文字或图片即可继续当前会话。': 'Send text or an image directly to continue the current session.',
+  '直接发送文字、图片或文件即可继续当前会话。':
+    'Send text, an image, or a file directly to continue the current session.',
+  '直接发送文字、图片、文件或带文字识别结果的语音即可继续当前会话。':
+    'Send text, an image, a file, or a voice message already transcribed to text to continue the current session.',
+  '{label}机器人已连接 DeepSeek Harness。': 'The {label} bot is connected to DeepSeek Harness.',
+  '/new  开启一个全新会话': '/new  Start a brand-new session',
+  '/compact  压缩当前会话的较早上下文': '/compact  Compact the earlier context of the current session',
+  '/workspace 工作区绝对路径  切换工作区': '/workspace <absolute workspace path>  Switch workspace',
+  '/workspacelist  列出工作区绝对路径': '/workspacelist  List absolute workspace paths',
+  '/sessionlist [工作区序号或绝对路径]  列出会话 ID 和标题':
+    '/sessionlist [workspace index or absolute path]  List session IDs and titles',
+  '/session Session ID 或当前工作区序号  将当前聊天绑定到指定会话':
+    '/session <Session ID or workspace index>  Bind this chat to the specified session',
+  '/models  按序号列出所有可用模型': '/models  List all available models by index',
+  '/model [序号或完整模型ID]  查看或切换当前会话模型':
+    '/model [index or full model ID]  Show or switch the model of the current session',
+  '示例：先发 /models，再发 /model 2': 'Example: send /models first, then /model 2',
+  '/presetlist  按序号列出可用 Agent Preset': '/presetlist  List available Agent Presets by index',
+  '/preset [序号或完整ID]  查看或设置当前机器人 Agent Preset':
+    '/preset [index or full ID]  Show or set the Agent Preset of this bot',
+  '纯数字 ID：/preset id:<ID>': 'Numeric-only ID: /preset id:<ID>',
+  '/preset --default  跟随 Host 默认': '/preset --default  Follow the Host default',
+  '/stop  停止当前任务': '/stop  Stop the current task',
+  '/steer 补充指令  纠偏当前任务': '/steer <additional instruction>  Steer the current task',
+  '/status  检查连接状态': '/status  Check the connection status',
+  '/help  显示本帮助': '/help  Show this help',
+  '{label}机器人与 DeepSeek Harness 连接正常。':
+    'The {label} bot is connected to DeepSeek Harness and working normally.',
+  '已开启新会话。请发送你的问题。': 'A new session has started. Please send your question.',
+  '正在使用{name}…': 'Using {name}…',
+  '已停止。': 'Stopped.',
+  '请用文字回答当前问题。': 'Please answer the current question with text.',
+  '{label}交互问题发送失败。': 'Failed to send the {label} interaction question.',
+  '回答提交失败。': 'Failed to submit the answer.',
+  '回答提交失败，请重新发送当前问题的答案。':
+    'Failed to submit the answer. Please resend your answer to the current question.',
+  '检测到这个 Session 中遗留的待回答问题，已安全取消并继续处理你刚才的消息。':
+    'A pending question left over in this Session was detected. It has been safely cancelled, and your latest message is being processed.',
+};
+