Copy and past does not work for files on resource packages (linux / wayland)

### Apache NetBeans version

Apache NetBeans 19 release candidate

### What happened

When I want to copy a file and paste it into any test resource package of a maven project the message `Code is not a valid class` is shown and the file is not copied.

### How to reproduce

* Create a maven project
* Create a test resources folder
* Open Nautilus
* Right click a file -> Copy
* Right click the resources folder `` in NetBeans -> Paste

(When you paste on the `src/test/resources` node it's working)

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Arch Linux, Sway

### JDK

OpenJDK 64-Bit Server VM Temurin-17.0.8+7

### Apache NetBeans packaging

Apache NetBeans binary zip

### Anything else

_No response_

### Are you willing to submit a pull request?

Yes

Reproduce the issue with a Maven project, a test resources folder, and a file copied from Nautilus, then inspect the NetBeans project-tree paste handling for the resource node. Done means the file pastes there without the “Code is not a valid class” message, while pasting on the src/test/resources node continues to work.

Written by the indexing model from the issue text.