Agents: initial session list focus shows no indication

[TylerLeonhardt]

Testing #309100

Steps:

• Reload a window (important)
• Tab to sessions list on the left
• 🐛 nothing has initial focus

In the video you see me tabbing and shift tabbing. Notice you only see indication in the "New" button at the top, and the Customizations header at the bottom. The list in the middle only shows indication once you do arrow keys.

Screencast.from.2026-04-13.12-38-07.webm