Add bulk close options

[dst1213]

Summary

• Add a single confirmation dialog when closing multiple unsaved files, with Save All, Discard All, and Cancel options.
• Keep the existing per-file Save / Discard / Cancel dialog for a single unsaved file.

Screenshot

The multi-file unsaved changes dialog shows Discard All, Cancel, and Save All actions in one prompt.

Testing

• Not run locally after removing the SingleApplication patch; final diff is limited to the bulk close dialog behavior.

[dst1213]

[dail8859]

Patch the pinned SingleApplication dependency to avoid QNativeIpcKey on Qt 6.6+, fixing macOS shm_open bad name startup failures.

Can you remove this for now. The SingleApplication has other known problems with >= Qt6.6 (which is why this app is still using Qt6.5) and these changes should be submitted to that project.

[dst1213]

Patch the pinned SingleApplication dependency to avoid QNativeIpcKey on Qt 6.6+, fixing macOS shm_open bad name startup failures.

Can you remove this for now. The SingleApplication has other known problems with >= Qt6.6 (which is why this app is still using Qt6.5) and these changes should be submitted to that project.

Ok, done

[dail8859]

Oops referenced wrong issue.