core: reset sgr on deinit, and at the end of prettyPrint

Reset SGR unilaterally when deiniting vaxis. Also reset it at the end of
a prettyPrint render.

src/Vaxis.zig

···
 
     // always show the cursor on exit
     tty.writeAll(ctlseqs.show_cursor) catch {};
+    tty.writeAll(ctlseqs.sgr_reset) catch {};
     if (self.screen.cursor_shape != .default) {
         // In many terminals, `.default` will set to the configured cursor shape. Others, it will
         // change to a blinking block.
···
     try tty.writeAll(ctlseqs.sync_set);
     defer tty.writeAll(ctlseqs.sync_reset) catch {};
     try tty.writeAll(ctlseqs.sgr_reset);
+    defer tty.writeAll(ctlseqs.sgr_reset) catch {};
 
     var reposition: bool = false;
     var row: usize = 0;