Research: Audit Notebook error messages/instructions

We've received feedback that the existing error messages/help text are confusing and that there need to be more helpful instructions. We need to audit all of the user error messages that currently exist and find any errors that users could run into that still need a message. Outside of error messages, let's determine where we might need better instructions as well.

We need to treat error message language and visual representation consistently. Users can receive an error message via a notification in the top right or message within the panel itself.