M4: Telegram bot channel

[bug-ops]

Goal

Zeph accessible via Telegram bot, with CLI as fallback.

Scope

• Channel trait abstraction
• CLI channel (wrap existing)
• Telegram adapter (teloxide)
• Bot commands: /start, /reset, /skills
• User whitelist

Acceptance Criteria

• With ZEPH_TELEGRAM_TOKEN: starts as Telegram bot
• Without token: falls back to CLI
• Telegram messages get LLM responses
• Bot commands work
• Unauthorized users blocked

Child Issues

• Define Channel trait and wrap CLI in it #21 Define Channel trait and wrap CLI in it
• Implement Telegram bot adapter with teloxide #22 Implement Telegram bot adapter with teloxide

Depends On

#4 (M3)