Feature Request: Add leave/mute/delete endpoints for chat management

[turian]

Request

Expose existing Beeper app functionality in the Desktop API:

• chats.leave() - Leave group chats
• chats.mute() / chats.unmute() - Mute/unmute notifications
• chats.delete() - Delete chat (already in app since Oct 2025)
• chats.set_low_priority() - Mark as low priority

Why

Many API users are refugees from fragmented messaging—we've accumulated group chats across WhatsApp, Telegram, Signal, Slack over years.

The API is excellent for inbox triage (read, prioritize, reply), but we can't complete the workflow without leaving/muting the noise. Currently requires switching to the app for each unwanted group.

Notes

• These features already exist in Beeper apps
• Just need REST API endpoints to match
• Would enable full inbox-zero workflows via API/CLI tooling