fix: the selected row has a background in every pane, not only the focused one

Bold alone was hard to see without a theme, so the other panes didn't
show what was selected in them.

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

docs/config.md

@@ -56,7 +56,7 @@ theme:
   activeBorderColor: ["#ff966c", bold]   # focused pane
   inactiveBorderColor: ["#589ed7"]
   selectedLineBgColor: ["#2d3f76"]       # cursor row background (default: palette 8)
-  inactiveViewSelectedLineBgColor: ["#2f334d"]
+  inactiveViewSelectedLineBgColor: ["#2f334d"] # in the other panes (default: palette 8, not bold)
   defaultFgColor: ["#c8d3f5"]
   optionsTextColor: ["#82aaff"]          # keys and labels
   searchMatchColor: ["#ffc777", bold]