Expose a SystemVirtualTerminal.DangerousRestoreSettings method.

Fixes #1.

src/core/Drivers/TerminalDriver.cs

@@ -192,6 +192,8 @@ public void DisableRawMode()
         lock (_rawLock)
             SetRawMode(IsRawMode = false);
     }
+
+    public abstract void RestoreSettings();
 }
 
 abstract class TerminalDriver<THandle> : TerminalDriver

src/core/Drivers/Unix/LinuxTerminalDriver.cs

@@ -83,6 +83,12 @@ protected override void SetRawModeCore(bool raw, bool flush)
             throw new TerminalException($"Could not change raw mode setting: {new Win32Exception().Message}");
     }
 
+    public override void RestoreSettings()
+    {
+        if (_original is termios tios)
+            _ = tcsetattr(TerminalOut.Handle, TCSAFLUSH, tios);
+    }
+
     public override int OpenTerminalHandle(string name)
     {
         return open(name, O_RDWR | O_NOCTTY | O_CLOEXEC);

src/core/Drivers/Unix/MacOSTerminalDriver.cs

@@ -87,6 +87,12 @@ protected override void SetRawModeCore(bool raw, bool flush)
             throw new TerminalException($"Could not change raw mode setting: {new Win32Exception().Message}");
     }
 
+    public override void RestoreSettings()
+    {
+        if (_original is termios tios)
+            _ = tcsetattr(TerminalOut.Handle, TCSAFLUSH, tios);
+    }
+
     public override int OpenTerminalHandle(string name)
     {
         return open(name, O_RDWR | O_NOCTTY | O_CLOEXEC);

src/core/Drivers/Windows/WindowsTerminalDriver.cs

@@ -145,6 +145,15 @@ protected override void SetRawMode(bool raw)
         SetRawModeCore(raw, true);
     }
 
+    public override void RestoreSettings()
+    {
+        if (_original is var (inMode, outMode))
+        {
+            _ = SetConsoleMode(TerminalIn.Handle, inMode);
+            _ = SetConsoleMode(TerminalOut.Handle, outMode);
+        }
+    }
+
     public override unsafe bool IsHandleValid(SafeHandle handle, bool write)
     {
         if (handle.IsInvalid)

src/core/SystemVirtualTerminal.cs

@@ -64,4 +64,13 @@ public override void DisableRawMode()
     {
         _driver.DisableRawMode();
     }
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public void DangerousRestoreSettings()
+    {
+        // This method is named as it is and hidden from IntelliSense because restoring the original terminal settings
+        // and then calling any I/O method in our API could have completely unpredictable results. Nevertheless, we
+        // expose the method for people who know what they are doing.
+        _driver.RestoreSettings();
+    }
 }