[IMS] Cross-site and token behavior understanding

As a customer and maintainer of DA, I would like a better understanding of the following:

1. What determines my default org when I revisit DA after a period of time? The perception is that visiting DA after a period of time defaults you into an org vs picking up the last used org.
2. What is the relationship between other sites and DA? Due to IMS having different integration types, it appears org switching and logging out has different implications depending on what surface is being logged out of. DA has an integration more similar to `adobe.com`, while `experience.adobe.com` seems to use a more server-side approach. The goal would be to throughly document across the common surfaces to understand how logging out affects DA and the user.
3. Get specific about refresh tokens and expiration. What happens when and why. If I don't use DA for two weeks, what happens?
4. Map behaviors back to how these different events should be handled by DA.

No files, tests, or entry points are named. Start by tracing the IMS behavior across DA, adobe.com, and experience.adobe.com, then document default-org selection, logout and org-switching effects, and refresh-token expiration, including the expected DA handling for each event.

Written by the indexing model from the issue text.