Create experimental visual editor toolbar & services

[wwwillchen]

Feature overview

• You can drag it around and expand/minimize which is persisted into localStorage.
• You can view history and revert to a previous revision
• You can save a change from the view history which it adds to goldens/

Eng Design

• The visual editor toolbar is guarded behind a flag and lazily loaded with defer views because it's still in an experimental stage and we don't want to load it for other Mesop app developers.
• This also separates the LLM call into a separate service because we want to decouple it from the main Mesop package.

Usage

Server-side

cd ai/services/
pip install -r requirements.txt 
python service.py 

Client-side

Flag control (run in chrome devtools console):

Enable:

window.localStorage.setItem('MESOP://SHOW_EDITOR_TOOLBAR', 'true');

Disable:

window.localStorage.removeItem('MESOP://SHOW_EDITOR_TOOLBAR');

[richard-to]

LGTM

[richard-to]

[nit] Could be wrong, but think you can return error_message, status But I think what's here is a bit more clear.