Wide content rows (slider rows in audio / monitor panels) opted out of
the cursor fill by setting fill: "transparent" on their CursorSurface,
which left them with no cursor visual at all — j/k landed there
silently with no way to know what was selected.
Add an `outline: bool` flag to CursorSurface. When true, hasCursor
paints an accent border (Style.focusBorderColor at
Style.focusBorderWidth) instead of a fill, leaving the row's chrome
fully visible underneath. Use for slider rows where a fill would
obscure the track.
Audio output / input slider rows and the monitor brightness row opt
in. The dev gallery's slider section replaces its bespoke Rectangle
wrapper with the same CursorSurface { outline: true }, so what the
gallery documents is what the panels ship.
Ryan Hughes