feat(channels): add Telegram channel integration with ACP bridge

Implements the channels infrastructure for connecting external messaging
platforms to Qwen Code via ACP. Phase 1 supports plain text round-trip:
Telegram user sends message -> AcpBridge -> qwen-code --acp -> response
back to Telegram.

New packages:
- @qwen-code/channel-base: AcpBridge, SessionRouter, SenderGate, ChannelBase
- @qwen-code/channel-telegram: TelegramAdapter using telegraf

CLI: `qwen channel start <name>` reads from settings.json channels config,
spawns ACP agent, connects to Telegram via polling.

esbuild.config.js

@@ -62,6 +62,10 @@ esbuild
         __dirname,
         'packages/cli/src/patches/is-in-ci.ts',
       ),
+      '@qwen-code/web-templates': path.resolve(
+        __dirname,
+        'packages/web-templates/src/index.ts',
+      ),
     },
     define: {
       'process.env.CLI_VERSION': JSON.stringify(pkg.version),