feat: add Telegram private messaging channel

Connect a user-created Telegram bot to channel projects with encrypted credentials, numeric sender allowlists, unified execution and text replies. Use Electron networking for system proxy support, with polling recovery, cancellable delivery retries and live status updates.

Add schema 61 channel support, lifecycle regression tests, Electron integration probes and feature documentation. Require the performance principles in AGENTS.md and record three alternating baseline/current Main benchmark rounds.

Validation: typecheck, lint and diff checks passed. Full suite: 6087 passed, 87 skipped, one intermittent inline-help Electron failure that passed unchanged in isolation. Real Bot plus model acceptance remains pending; the local TLS proxy probe is opt-in.

Release note: 新增 Telegram 私聊通道，可配置 Bot Token 和用户白名单，通过通道项目处理文字请求并回复结果。支持系统代理、断线重连和停用取消；真实 Bot 与模型的完整联调仍待完成。

FEATURES.md

@@ -931,12 +931,13 @@ records are listed separately and do not introduce another feature status.
   action errors.
 - [x] **Client-computer control tools**: Managed separately from the built-in
   browser with scope, cancellation, timeout, output, and activity boundaries.
-- [x] **Remote messaging-channel projects**: WeChat ClawBot, WeCom, and
-  DingTalk each have a system-managed project, independent remote
+- [x] **Remote messaging-channel projects**: WeChat ClawBot, WeCom,
+  DingTalk, and Telegram each have a system-managed project, independent remote
   conversations, working directory, processing backend, and
   task/activity ownership. Each channel controls complete-response
   length and segmentation according to platform capabilities rather than
-  relying on a shared service truncation.
+  relying on a shared service truncation. Telegram's live Bot + model chain
+  remains [pending acceptance](./docs/features/telegram-channel/progress.md).
 - [x] **WeChat ClawBot QR login and media**: A separate Sidecar handles local
   QR scanning, verification codes, encrypted credentials, and text messaging.
   Personal WeChat chats support images and files, with at most four