The dim text token (disabled buttons, placeholders, hints) was 2.1:1 on
the light theme's panels; disabled buttons also faded to 40% opacity,
and selected text was drawn in the dark green, 1.4:1 on the dark
theme's selection highlight. The dim text token is now at least 3:1
against panels, fields and selected rows in both themes while staying
dimmer than secondary text, a disabled button is grey with that text,
and selected text takes the theme's readable green. A test checks the
ratios with the colour contrast helper.