BUILT.md appends and never dates, so a paragraph that was true when it was
written reads as fact forever. Two are not: the map type spelling is (Map K V)
and braces in type position are refused by name, and sand.flan has not called
load-texture since it was cut back to port parity. Both get the parenthetical
the FLAN_RAYLIB_H paragraph already got rather than an edit, since that is the
convention the file has.
SPIKE-GENERICS.md gets the treatment overview.md has: a header saying what it is
and when it stopped being current. Its body stays. The two things in it that
would now mislead are named there -- its account of what plan.org says, which
plan.org has since overtaken, and the bare-t-at-every-use rule, which is narrower
than what shipped, since (Option t) does not compile.
