Exercises match/yield/?/!/alloc/free/slice/tagged-union end-to-end:
the @symbol FFI binds initscr/mvaddch/init_pair/getch/napms; setup
returns (*void | initerr) propagated via `?`; main unwraps the clock
via `!`; dispatch is a nested match-as-expression that yields a
bool; key handlers fold into switch/enum (q/space) and (i32 |
speederr | void) for 1..4 + the '0' error overlay.
No definite or indirect leaks under valgrind (the only "possibly
lost" / "still reachable" bytes are libncurses's process-lifetime
terminfo caches, freed only with --with-leaks).
