Drag and drop to app icon doesn't open file in Audacity 4

Bug description

A typical Mac usage pattern is to drag a compatible audio file to the app icon in the Finder or Dock in order to open and edit that file. This doesn't appear to be happening on my machine, M1 Pro MBP 32/1T Tahoe 26.6.2, but works as expected in Audacity 3.7.7.

Steps to reproduce

1. Drag an mp3 file onto the Audacity 4.0 icon, either in the Finder or in the Dock

Expected behavior

The dragged file should open Audacity if it isn't already open, and load the file for editing.

Actual behavior

Nothing happens when you drag the file over Audacity 4's icon.

Audacity Version

Audacity 4.0.0

Operating system

macOS

Additional context

No response