Support system-level Do Not Disturb (DND) mode on Linux and Windows

Summary

Request to add support for system-level Do Not Disturb (DND) mode on Linux and Windows. When the operating system's DND mode is enabled, the client could optionally reflect this automatically.

Proposed Behaviour

• Detect when the OS-level DND mode is active (on Linux and Windows).
• Optionally change the user's presence status to DND automatically when the system DND mode is enabled.
• Suppress notification sounds and visual notifications while system DND is active.
• Make this behaviour optional/configurable.

Context

• Monitoring OS-level DND mode is reportedly not available to apps on macOS, so this request targets Linux and Windows.
• No specific handling for OS DND mode currently exists in the client.
• Pointers or implementation references for other OSs would be welcome.

Expected vs. Actual

• Expected: The client can optionally honour the system DND mode by adjusting presence and suppressing notifications/sounds.
• Actual: No OS DND mode integration exists.

No implementation files, tests, or entry points are named. Start by locating the client’s existing presence and notification handling, then investigate usable system DND signals on Linux and Windows; done means the behavior is optional and presence, sounds, and visual notifications respond correctly.