Dark-mode buttons fail non-text contrast; label chip colours are unchecked #120

style.css:120 keeps --fill: #0000f0 in dark and style.css:1288 gives button no border, so a button edge on #0a0a0a sits around 1.3:1 against WCAG 1.4.11's 3:1. web.go:1481 accepts any #rrggbb label colour and writes it as chip text colour (style.css:988), so a user-set #ffff00 label is illegible on white.

Remedy: a 1px --accent border on dark buttons; use the label hue for chip border and ground with --fg text.