Update past subgoal and action format

* **Feature description:** (Example: Add an exit button)
The past subgoals and actions are currently displayed via the sidebar tree. These links open the corresponding information in the slider but should open popup windows (like that of the persona facet popups). There should also be an option to open the corresponding screenshot.

* **Reason for the feature or improvement:** (Example: there is no right way to exit from the application)
The existing implementation is hard to navigate and read.

* **How does your idea fit with the aim/scope of the project?** (Example: feature gives the workflow)
Helps the user to see their past work during the session so they can reference past conversations.

* **What are the merits of the feature?** (Example: prevent data loss)
Ease of use, easier navigation, consistency

* **Screenshots, if you can show something similar, or a sketch:**