feat(telegram): support group bot mentions and replies

[me2seeks]

• add allowed_bot_users support to Telegram config parsing and the launcher-generated managed config template
• allow group and supergroup messages to target the bot by explicit mention or by replying to the current bot
• preserve the existing group chat allowlist behavior and cover the new Telegram handling with TypeScript tests

Details

This change updates Telegram group message handling so the gateway can respond to approved bot senders and to user replies to the current bot, instead of only accepting direct mentions.
It keeps the existing group allowlist model in place:

• group chats must still be present in allowed_chats
• human senders must still be present in allowed_users
• bot senders must now be present in allowed_bot_users
  When a group message passes allowlist checks, it is now treated as targeting the current bot when either of the following is true:
• the message explicitly mentions the bot
• the message replies to a message previously sent by the current bot
  The change also updates the managed launcher template so newly initialized Telegram configs include allowed_bot_users = [] by default.

Testing

• cargo test -p opencode-gateway-launcher
• bun test packages/opencode-plugin/src/config/gateway.test.ts packages/opencode-plugin/src/telegram/*.test.ts packages/opencode-plugin/src/runtime/tool-activity.test.ts