What kinds of variables are actually reactive? i.e. what triggers a reactive update? I found that a normal map isn't, but a mobx observable is: [open notebook](https://www.typecell.org/@tennox/public/typecell-reactive-map-test~dAM8tpBRB5gSw) [Screencast from 2023-12-22 14-21-56.webm](https://github.com/TypeCellOS/TypeCell/assets/2084639/cacdd8a1-3b24-43b8-a2a2-3f361fabfd12)