agent sessions - some fixes when shown in chat view (#279542)

* agent sessions - hide container when no sessions

* agent sessions - preserve `description` between restarts from cache

* agent sessions - enable filtering only in sessions view

* agent sessions - keep track of sessions count for layout

* agent sessions - fix layout issues in chat view

* agent sessions - go back to removing sessions without requests from local provider

* agent sessions - padding for status on the left to offset from description

* agent sessions - hide sessions in chat vew when welcome shows