macOS: Racket threads do not run while dragging a slider%

Re. https://github.com/Bogdanp/racket-gui-easy/issues/63#issuecomment-3225228993.

As the title says, when dragging a slider, threads other than the eventspace thread are suspended. So, the threads in this example end up not running while dragging the slider (or while initiating a drag and holding the slider):

#lang racket/gui

(define f
  (new frame%
       [label "Test"]))

(define thd
  (thread
   (lambda ()
     (let loop ()
       (println `(value ,(thread-receive)))
       (loop)))))

(define tick-thd
  (thread
   (lambda ()
     (let loop ()
       (println 'tick)
       (sleep 1)
       (loop)))))

(define timer
  (new timer%
       [notify-callback
        (lambda ()
          (println 'timer-tick))]
       [interval 1000]))

(define s
  (new slider%
       [parent f]
       [label "Test"]
       [init-value 0]
       [min-value 0]
       [max-value 100]
       [callback (lambda (self _event)
                   (thread-send thd (send self get-value)))]))

(send f show #t)

Surprisingly, the timer% doesn't run either.

As a hack, I've tried setting up a display link to post dummy events between drag start and end (the display link is necessary because changed: does not fire if you just hold the slider after dragging), but that doesn't seem to help. Probably the right solution is a run loop source in queue.rkt for the event tracking mode, but I'm not sure how to do that.

Start with the provided racket/gui example and reproduce the suspension while dragging a slider on macOS. Then inspect queue.rkt and the event-tracking mode behavior; the issue suggests a run loop source may be relevant. Done means non-eventspace threads and the timer continue running during slider drags.