Guard against Rat positions in print commands

t/11-golf.t seems to manage to pass a Rat (`T.colums/2`) to
`T.print-string`. Unsure why this didn't fail earlier.

Author: patrickbkr

lib/Terminal/Print/Commands.pm6

@@ -30,7 +30,7 @@ my %commands =
 sub columns is export { Terminal::API::get-window-size().cols }
 sub rows    is export { Terminal::API::get-window-size().rows }
 
-sub move-cursor(Int $x, Int $y) is export {
+sub move-cursor(Int() $x, Int() $y) is export {
     "\e[{$y+1};{$x+1}H"
 }
 

lib/Terminal/Print/Grid.pm6

@@ -240,21 +240,21 @@ multi method cell(Str $char) {
 }
 
 #| Replace the contents of a single grid cell, specifying a hash with char and color keys
-multi method change-cell($x, $y, %c) {
+multi method change-cell(Int() $x, Int() $y, %c) {
     return unless 0 <= $x < $!w && 0 <= $y < $!h;
     $!grid-string = '';
     @!grid[$y][$x] = Cell.fast-create(%c<char>, %c<color>);
 }
 
 #| Replace the contents of a single grid cell with a single uncolored/unstyled character
-multi method change-cell($x, $y, Str $char) {
+multi method change-cell(Int() $x, Int() $y, Str $char) {
     return unless 0 <= $x < $!w && 0 <= $y < $!h;
     $!grid-string = '';
     @!grid[$y][$x] = $char;
 }
 
 #| Replace the contents of a single grid cell with a prebuilt Cell object
-multi method change-cell($x, $y, Cell $cell) {
+multi method change-cell(Int() $x, Int() $y, Cell $cell) {
     return unless 0 <= $x < $!w && 0 <= $y < $!h;
     $!grid-string = '';
     @!grid[$y][$x] = $cell;