Minor Bugs

**Collection of a few minor bugs**

- [ ] Nodes can be pasted to detached nodes. This should not be possible, since that is not the idea behind a mind map.
- [ ] If you type in a value higher than the max value in the font size options in the settings menu, it sets the value back to the default value. It would be expected to set the value to the max value instead
- [ ] The graphically indicated steps of the font size slider do not reflect the actual steps

Start by reproducing each of the three reported behaviors: pasting onto detached nodes, entering an oversized font value, and comparing the slider's visual steps with its actual values. Trace the node-paste and font-size settings entry points from the affected UI, then verify that detached-node pastes are blocked and both font-size behaviors match the stated expectations.

Written by the indexing model from the issue text.