Throw PlatformNotSupportedException when a signal can't be synthesized.

src/core/Terminals/Windows/WindowsVirtualTerminal.cs

@@ -88,8 +88,7 @@ protected override void SendSignal(int pid, TerminalSignal signal)
             {
                 TerminalSignal.Close => CTRL_CLOSE_EVENT,
                 TerminalSignal.Interrupt => CTRL_C_EVENT,
-                TerminalSignal.Quit => CTRL_BREAK_EVENT,
-                TerminalSignal.Terminate => CTRL_SHUTDOWN_EVENT,
+                TerminalSignal.Quit or TerminalSignal.Terminate => throw new PlatformNotSupportedException(),
                 _ => throw new ArgumentOutOfRangeException(nameof(signal)),
             },
             (uint)pid);