Collapse main.cpp's hand-written ladder of 28 individual
"if --foo and i+N >= argc, print message, return 1" blocks
into a single loop over kMultiArgRequired (struct of flag,
needed count, synopsis).
main.cpp drops from 246 → 126 lines. Adding a new multi-arg
flag now means appending one row to cli_multi_arg_required.cpp
instead of pasting another six lines into the validation
ladder. Mirrors the kArgRequired pattern that handles
single-arg flags.
