macOS: Scratch Desktop ignores document-open events for .sb3 files (Finder, open -b)

[dmb0058]

Expected Behavior

When a .sb3 file is opened using standard macOS mechanisms (e.g. Finder double-click, drag & drop, or open from Terminal), Scratch Desktop should open and load the specified project, in the same way that File → Load from my computer does.

Actual Behavior

Scratch Desktop launches successfully but always opens a new blank project, silently ignoring the .sb3 file that was requested to be opened. No error message is shown.

Steps to Reproduce

1. Install Scratch Desktop on macOS and ensure .sb3 files are associated with Scratch.
2. Create or obtain a valid Scratch .sb3 project file.
3. Attempt to open the file using any of the following methods:

• Double-click the .sb3 file in Finder
• Drag the .sb3 file onto the Scratch app icon or Dock icon
• Run the following command in Terminal:
  open -b edu.mit.scratch.scratch-desktop "/full/path/to/project.sb3"

4. Observe Scratch Desktop after it launches.

System Details

App: Scratch Desktop
Version: 3.31.1
Platform: macOS Sonoma 14.5
Installation path: /Applications/Scratch 3.app

Screenshots
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