Reproduces the renderer's pre-#5484 hardcoded look, so a caller that never
calls setOverlayTheme (a test, a standalone tool) sees no visual change:
the old selection blue, the old "down"-axis section-plane colour and
opaque-black overlay lines. The clash tints never had a renderer-side look
to preserve (every caller passed its own colour), so they are the viewer's
light-theme clash-a / clash-b / clash-overlap tokens (#5490) rather
than the retired amber / cyan / magenta.
Reproduces the renderer's pre-#5484 hardcoded look, so a caller that never calls
setOverlayTheme(a test, a standalone tool) sees no visual change: the old selection blue, the old "down"-axis section-plane colour and opaque-black overlay lines. The clash tints never had a renderer-side look to preserve (every caller passed its own colour), so they are the viewer's light-themeclash-a/clash-b/clash-overlaptokens (#5490) rather than the retired amber / cyan / magenta.