Deployment Manager UI improvements: clearer empty state and run activity messaging

AI Impact Summary

The Deployment Manager UI has been updated to handle empty and non-empty states more clearly. The agent list now renders with an empty class when there are no rows, and the empty state displays a stronger message: No apps deployed, plus guidance to deploy an Agents SDK app and inspect traces, including a concrete deployment command. The RecentRunsSummary timeline and grid visuals also adapt based on whether run data exists, surfacing an explicit message when there are no runs. These changes improve onboarding, reduce user confusion during first-time setup, and streamline inspection workflows by clarifying available actions and expected data paths.