`Show Agent Sessions Sidebar` doesn't appear on narrower editor instance

[bamurtaugh]

Ref https://github.com/microsoft/vscode-internalbacklog/issues/6527

• I was running two different instances of the same app in separate VS Code windows, side-by-side so that I could compare different agentic results on the same prompts
• ❓ Selecting Show Agent Sessions Sidebar didn't actually display the sidebar, which felt like an unexpected no-op (since I didn't think my editor instance was that narrow)

Delegation.1-8.4.mp4

I'm not sure if we can do much here, but I figured I'd still report it for discussion.

[bpasero]

A possible change to do here is to just maximize the 2nd sidebar in case the available space does not suffice.

[bpasero]

Pragmatic fix is to maximise the 2nd sidebar in these cases to ensure sufficient room for the side by side view.