numfmt: `--invalid=warn/ignore/fail` ignores mode when rejecting scientific notation

[sylvestre]

Summary

Follow-on to #11655. Scientific-notation inputs are now correctly rejected in the default --invalid=abort mode, but the rejection path bypasses --invalid=warn/ignore/fail handling — uutils halts after the first invalid value and exits 2 regardless of the requested mode, while GNU prints the bad value, continues with the remaining inputs, and exits 0 for warn/ignore.

Regular invalid inputs (random garbage strings) behave correctly; only the scientific-notation rejection path is broken.

Found by fuzz_numfmt.

Reproduction

$ LC_ALL=C /usr/bin/numfmt --invalid=warn 100 1e5 200
100
numfmt: invalid suffix in input: '1e5'
1e5
200
(rc=0)

$ LC_ALL=C target/debug/numfmt --invalid=warn 100 1e5 200
100
numfmt: invalid suffix in input: '1e5'
(rc=2)

Same divergence for --invalid=ignore and --invalid=fail (for fail, both should exit 2 but GNU still prints all three numbers).

Sanity check — other invalid inputs handle --invalid=warn correctly:

$ numfmt --invalid=warn 100 garbage 200   # both print all three, rc=0