Session title, details, source, provider, state and age text lived on the
applet root although only SessionsView reads it. SessionLabels now owns
those six localized functions beside the view, which exposes it as
`labels` for the smoke capture. The catalog test instantiates it directly
instead of extracting function bodies from main.qml.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>