Agents window detail panel: Files list missing in existing folder sessions

[bamurtaugh]

Testing #324359

• Start on new session screen
• Select an existing folder (non-worktree) session
• Session populates as expected from its previous state I left it in

• I decide to switch over to the Files tab
• ❓ No files listed, and I'm unclear how to get back to them

• If I select previous worktree sessions instead, their files populate:

[bamurtaugh]

I discovered I can use the Toggle Details button in the top right, but that then hides the session list on the left, and I'd need to Toggle Side Bar to get the primary sidebar with the session list to appear again. I'm not sure why the default file and session listing behaviors seem to differ for worktree vs folder sessions? Or did I somehow get myself into this state?