Without an after-separator state, the new unknown-flag guard rejected
flag-shaped prompts (`omp -p -- --explain-this`): the loop dropped the
`--` token and then re-validated `--explain-this`, recorded it in
`unrecognizedFlags`, and exited 2.
parseArgs now flips a `sawSeparator` latch on `--` and short-circuits
the remaining tokens straight into `messages` — no built-in dispatch,
no extension match, no `@file` expansion. Two regression tests cover
the flag-shaped and `@`-prefixed cases.
Refs #2459
roboomp
cd87b82ac0