Make Healthcheck issue rows compact

[astandrik]

Implement the compact Healthcheck issue rows from #4448 (design reference).

• Place a soft, icon-only status label before the issue title; show the status name in a tooltip and expose an accessible name.
• Keep the existing action and expand/collapse controls on the right, with details below. Long titles must wrap without pushing the controls out of view.
• Cover rows with and without assistant actions in light and dark themes. Preserve default status labels elsewhere.

This is a layout change in the shared UI package. It uses the existing healthcheck.renderAssistantAction extension; no assistant wiring or backend changes are needed. Diagnostics/Fix button styling and the chat welcome screen belong to the separate assistant task.