watchdog 7.0.0 on Windows starts a plain threading.Thread per watch for
its ReadDirectoryChangesW reader (DirectoryChangeReader.start). Created
from ComfyUI's main thread it is not a daemon, and the interpreter joins
every non-daemon thread before it runs any atexit callback, so the
package teardown that would stop the observer never ran and the process
never exited.
Start the observer from a short-lived daemon thread, so every thread it
creates inherits the daemon flag. Run observer.stop(), which joins the
emitters without a limit, on a daemon thread and wait for it only until
the stop deadline; a later stop waits for the same call. Lift the
watchdog<7 cap.
Closes#561
Vito Sansevero
c791e2481a