UX Experiment - editor wide content lock

[getdave]

What?

Tries applying contentOnly mode to all top level sections

Why?

This is just an experiment to see how it feels if we make all the blocks within the top level sections content only. This makes the editor feel a lot more simple.

How?

To make this easy to test, i've shoehorned in a Simple mode into the mode selector at the top of the editor. This is only for testing purposes!

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

https://github.com/user-attachments/assets/53474810-5b2c-492c-a9e9-d41b142ebc5b