Clipboard contents not recognized when pasting from macOS system clipboard

[hubble63]

System

• GanttProject version: 3.3.3316 (latest)
• macOS version: 15.4.1 (Sequoia)
• Hardware: MacBook Pro (Apple Silicon)

Issue

When I copy any plain text from another application (TextEdit, Safari, Notes, etc.) using Cmd+C and try to paste it into a GanttProject input field (e.g. task name or notes), the paste action does not work. GanttProject seems to ignore the macOS system clipboard contents entirely.

Steps to reproduce

1. Open GanttProject
2. Focus on a text input field (e.g. "Task name")
3. Copy any text using Cmd+C from another macOS app
4. Use Cmd+V or right-click → Paste inside GanttProject
5. Nothing happens – clipboard is ignored

Notes

• This problem is reproducible on multiple macOS versions including Ventura and Sequoia.
• The clipboard works in other Java apps, so this appears to be a specific compatibility issue with GanttProject.
• This bug makes automation or external tools (like Shortcuts, AppleScript, Keyboard Maestro) ineffective for pasting data into GanttProject.

Expected

Text from macOS clipboard should be inserted as expected.