Add AutoPilot mode + multi‑channel integrations

### Describe the feature or problem you'd like to solve

Copilot CLI to operate semi‑autonomously (like Clawdbot/Moltbot) and be reachable via Teams/WhatsApp/Discord/etc while remaining secure and opt‑in.

### Proposed solution

- Add copilot autopilot command group to install/start a background daemon and a /autopilot interactive mode
- Local IPC (localhost HTTP/WS or local socket), approval gates, tool allowlists, sandbox for non‑main sessions
- Channel connectors via MCP/plugin interface; initial adapters: Microsoft Teams, Discord, Slack, WhatsApp, Telegram, Google Chat, Signal, iMessage, etc.

How will it benefit GitHub Copilot CLI and its users?

- Hands‑free multi‑channel assistant while preserving explicit‑approval safety
- Long‑running workflows and monitoring without leaving the CLI
- Extensible integration surface for community‑built connectors

### Example prompts or workflows

- "Autopilot, triage new Discord messages and open GitHub issues when bugs are reported"
- "Listen on WhatsApp for on‑call keywords, run diagnostics, and ask me before applying fixes"
- "From Slack, summarize last 24h PR activity and draft a status update"
- "From Teams, answer repo setup questions and link relevant docs"
- "From Telegram, run the release checklist and pause for approvals"

### Additional context

_No response_