Five smoke tests covering the canonical cyclone-cli pattern:
1. --help renders cleanly and lists every long-form flag from the
SP24 spec §2 Decision 3.
2. happy path: a single-file input dir produces 1 .x12 file +
_serialize_summary.json sidecar; CLI exits 0 with the
'DONE files=1 errors=0' summary line in stdout.
3. empty input dir: CLI exits 2 with a 'PARSE FAILED' message in
stderr (matches the spec's exit-code contract).
4. IG-correctness guard: monkeypatches serialize_837.
PATIENT_LOOP_DEFAULT_INCLUDED to True; CLI exits 1 with
'REFUSING to run' in stderr.
5. --zip-output: the resulting zip's testzip() returns None;
entries round-trip with the HCPF-spec filename shape.
Also fixes the datetime import in cli.py (was using bare datetime.now()
which is undefined — switched to the existing _datetime alias) and
adds a 'no files found' error path to cyclone.reissue.parse_inputs
so empty input dirs surface as exit 2 rather than exit 0.
Nora