Make panel "sticky" so it starts and stays open in Edit mode

> Scanning the rest of the items. I think those fixes will help solve many of the issues. These though look more like design or research questions?
> - "Investigate possibility of having the panel stick open in Edit mode (open by default) and only close if it's shut off intentionally (rather than closing everytime you navigate elsewhere)"
> - Small dev lift

_Originally posted by @thiessenp-cds in [#6015](https://github.com/cds-snc/platform-forms-client/issues/6015#issuecomment-3267382751)_

Start by tracing the Edit mode panel behavior and how navigation affects its open or closed state. Confirm the desired behavior: the panel opens by default, stays open while navigating in Edit mode, and closes only when intentionally shut; no files or tests are named in the issue.

Written by the indexing model from the issue text.