Expose notification commands in control bridge

[mvbmir]

Goal

Wire notification commands from limux-core through the control bridge socket.

Missing Commands

• notification.create - Create a desktop notification from an external tool
• notification.list - List pending notifications
• notification.clear - Clear notifications
• notification.create_for_surface - Create notification tied to a specific surface

Use Cases

• Claude Code agents notifying the user when a long task completes
• Scripts sending notifications through the limux socket instead of notify-send
• Surface-specific notifications (e.g., "build failed in workspace X")