-- Unknown `--flag` shapes in the positional tail are rejected upfront
-- with a clear "unrecognised flag" error and exit 1, instead of being
-- silently consumed as positional args (which used to surface as
-- misleading ILO-R012 "no functions defined" or ILO-R004
-- "main: expected N args, got N+1"). Six rerun8 personas independently
-- burned minutes on the old trap.
--
-- To pass a hyphen-prefixed token as a literal arg, separate with `--`
-- first: `ilo main.ilo -- --foo`. Anything after the first `--` is data.
--
-- The happy-path example below is exercised via the engine harness so
-- the unknown-flag guard's no-op behaviour on plain positional args
-- stays under cross-engine regression coverage.
main x:n>n;+x 1
-- run: main 41
-- out: 42