fix: windows: ensure the input buffer is empty

Before initializing the input reader, we need to ensure that
the console input buffer is empty, otherwise, we can get dangling
events from previous sessions.

cancelreader_windows.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	xwindows "github.com/charmbracelet/x/windows"
 	"github.com/muesli/cancelreader"
 	"golang.org/x/sys/windows"
 )
@@ -47,6 +48,11 @@ func newCancelreader(r io.Reader) (cancelreader.CancelReader, error) {
 		return fallback(r)
 	}
 
+	// Discard any pending input events.
+	if err := xwindows.FlushConsoleInputBuffer(conin); err != nil {
+		return fallback(r)
+	}
+
 	originalMode, err := prepareConsole(conin,
 		windows.ENABLE_MOUSE_INPUT,
 		windows.ENABLE_WINDOW_INPUT,