Disable keyboard shortcuts in text entry

**Is your feature request related to a problem? Please describe.**
When I'm entering minutes, I hit C-b and it turns on bold text and (in markdown mode) inserts `****`

**Describe the solution you'd like**
I'd like to turn that off. Default macos keybindings use that for "back one character" which makes it annoying while typing

**Describe alternatives you've considered**

Several options:
- Teaching myself to type differently is one alternative. Definitely not fun to have to move to the arrow keys or learn some new key layout though.
- Browser extensions can block specific hooks on some websites. I've played around with these but editing the page javascript is obviously quite fragile.
- I can type my notes somewhere else and paste them in.

**Additional context**

In general having text entry hijack your system keybindings seems like an option you should be able to turn off. Maybe it's there and I didn't see it, in which case sorry for the noise.

The issue names no files, tests, or entry points. Start by locating the text-entry and keyboard-shortcut handling, then determine how markdown mode is involved; done means text entry no longer hijacks the requested system keybindings while existing editing behavior remains intact.

Written by the indexing model from the issue text.