Document textarea filter, better message when no profile exist

Problem/Motivation

From #3622638: bug: Recipe install leaves Display Builder without its default profile (config/optional not applied):

• Document the config: import line for recipe authors, and fix docs/textarea.md, which currently says the format is always created.
• Replace the misleading "You are not allowed to use Display Builder" message when no profile exists with a clear hint and a link to create one.