Add channel connector

[codeaholicguy]

Summary

• Add new @ai-devkit/channel-connector package, a generic messaging bridge that connects to external platforms (Telegram first)
• Add CLI channel commands (connect, list, disconnect, start --agent, status) that wire channel-connector with agent-manager to enable two-way agent communication from Telegram

Key design decisions:

• Decoupled packages: channel-connector knows nothing about agents; CLI bridges both
• Async non-blocking flow: input fires-and-forgets to agent, separate polling loop pushes output back
• One agent per session: channel start --agent binds one Telegram bot to one agent
• Auto-authorize first user: no config step for chat ID

CLI commands

• ai-devkit channel connect telegram — interactive bot token setup with validation
• ai-devkit channel list — show configured channels
• ai-devkit channel disconnect telegram — remove config
• ai-devkit channel start --agent — start bridge (foreground)
• ai-devkit channel status — show config status