Fields in 'plot' can be detached but not reattached

Describe the bug

If you have a 'plot x,y' block you can detach it with the shortcut key 'x'. Pressing 'undo' moves it back to approximately the original position but does not reconnect it. Ctrl+C to copy it claims success, but you can't paste it back in the original connection. Once detached, you can't actually delete it at all.

To Reproduce

1. New project
2. Turn on keyboard controls
3. Add 'plot x,y' block
4. Edit x and y fields to whatever numbers (optional - same behaviour either way)
5. Press 'x' to detach
6. Press Ctrl+Z to undo
7. OBSERVE: it moves back but doesn't reconnect
8. Use arrows to select the orphaned block and Ctrl+C
9. Use arrows and Ctrl+V to try to paste it back
10. OBSERVE: you can't put it back
11. Use arrows and Del to try to delete it
12. OBSERVE: you can't delete it

Expected behavior

You should either not be able to detach it, or should be able to undo the operation and copy/paste it.

Screenshots

micro:bit version (please complete the following information):
not relevant

Desktop (please complete the following information):

• OS: win 11
• Browser: Chrome and Firefox

Start by reproducing the issue in a new project with keyboard controls enabled, following the listed detach, undo, copy/paste, and delete steps. Trace the editor entry points handling the 'plot x,y' block and these keyboard operations; done means the block can either not be detached or can be reconnected, copied, pasted, and deleted after detaching.