- Add Telegram handling to relay command when selected via pickProvider
- Add Telegram delivery support to agent --deliver command
- Add telegram: prefix to sender identifiers to prevent session ID collisions
- Update detectProvider to properly handle telegram: prefixed identifiers
- Document provider detection logic and session ID collision prevention
Fixes session ID collisions where Telegram users without usernames (numeric IDs
or phone numbers) were being misidentified as WhatsApp users, causing cross-
provider session leakage.