The params text of ui.layersPanelOptions and the doc comment on
PanelOptions::locate_selected said that, with the option on, the panel
opens the rows around any object selected outside it and scrolls to its
row. When Show Layers Only, a search or the filter leaves the object
without a row, the panel opens no rows for it and scrolls as with the
option off. Both texts now describe that case, as docs/mcp.md does.