v0.1.0-alpha.66

Lightty's terminal text is visible again. Its palette was a dark-theme
ramp with the background flipped to white: nine of sixteen slots sat
under 4.5:1 and slot 15 was white on white at contrast 1.00. Shell
prompts write ordinary text in slots 7 and 15, so the terminal rendered
blank. The yellow slot also held a purple one step from magenta, which
broke colour-coded output.

The palette is recut against the same floors Nacre is held to, and the
test exemption that recorded these failures as acceptable is gone.