Dark shades map to black and greys to the grey/white entries while
saturated category colours keep their hue, instead of the stock
conversion's bright yellow/cyan shadows.
Decompression and checksumming overlap with parsing via a pipe, and a
concrete-typed varint reader removes per-byte interface calls
(0.39s -> 0.29s for 458K nodes).
--compare opens the TUI with growth/shrink colouring unless a report is
requested. treegen builds deterministic synthetic trees (Unicode,
hostile names, sparse files). MAPSIZE_DEBUG_PANIC verifies terminal
restoration on UI and scanner panics.
Andy Dixon