Desktop notifications via terminal OSC escape sequences.
Sends both OSC 777 (urxvt-style) and OSC 9 (iTerm2-style) for broad terminal compatibility. Supported by Ghostty, iTerm2, WezTerm, foot, kitty, and most modern terminals.
@spec notify(String.t(), String.t()) :: :ok
@spec task_completed(String.t() | nil) :: :ok
@spec task_error(String.t() | nil) :: :ok