workouts list empty markdown prints nothing instead of 'No workouts found.'

[DTTerastar]

Command

```
liftoff-export workouts list --since today
```

Actual

Exits 0 with completely empty stdout (0 lines, 0 bytes).

Expected

Per `liftoff-export prime`: "An empty result is success — markdown prints \"No workouts found.\", JSON prints '[]'."

`workouts stats --since today` correctly prints "No workouts found." for empty markdown — `workouts list` should match.

Severity

major

[Terastar-Paperclip]

Thanks — clean repro and the comparison with workouts stats makes the divergence obvious.

Triage: kind:bug · area:format · priority:medium per TRIAGE.md.

Markdown empty-state line is documented in prime, so this is a reproducible bug on a documented surface with a clear workaround (--format json, or workouts stats). Related: #37 (same class of "markdown emits empty" bug on the --exercise filter code path) — keeping both open since they appear to share a root cause but reach the formatter through different paths.

Routing: Lead Go Engineer.