Telegram plugin: per-session/per-project bot token support

Today the Telegram plugin stores one bot token at ~/.claude/channels/telegram/, shared by all Claude Code sessions on the machine. Running multiple concurrent sessions (e.g., different projects) requires separate OS users as the only clean workaround.

Requesting per-project or per-session bot token configuration so one machine can route different sessions to different bots/chats.

Use case: a user running several Claude Code sessions simultaneously across different projects wants each session to send/receive Telegram messages via a distinct bot, so notifications and replies stay scoped to the project they relate to.