Drag and drop of files to attach no longer works in the Copilot app (regression, macOS)

[kayone007]

Describe the bug

Dragging a file from Finder onto the GitHub Copilot app to attach it to a prompt no longer works. When a file is dropped on the prompt composer, nothing is attached: no attachment chip appears and no file path is inserted.

This is a regression. Drag-and-drop file attach worked in a previous release (the feature was originally added in #363), and after updating to a newer build it is broken again, back to the same behavior as before the feature existed.

Affected version

1.0.65

Steps to reproduce the behavior

1. Open the GitHub Copilot app.
2. Focus the prompt composer in a session.
3. Drag a file (for example an image PNG, or a text/source file) from Finder and drop it onto the composer.
4. Observe that nothing is attached: no attachment chip is shown and the file path is not inserted into the prompt.

Expected behavior

Dropping a file onto the composer should attach it to the prompt (show an attachment chip / insert the file path), the same way it worked in the release where this feature was functioning.

Additional context

• Operating system: macOS
• CPU architecture: arm64 (Apple Silicon)
• Regression: drag-and-drop file attach worked in an earlier release and stopped working again after a later update.
• Related history: Support drag/drop and copy paste of images into CLI #363 (drag/drop + paste of images added), Dragging macOS screenshot preview into Ghostty results in "Path does not exist" #2043 (related drag handling of a macOS screenshot temp path in a terminal).