fix: CLI error messages written to stdout instead of stderr

[namanyadav-08]

Bug Description

All CLI commands (test, import, import-url, import-dir) print
error messages to stdout instead of stderr. This is incorrect
Unix behavior and breaks CI/CD pipeline scripting where stdout
and stderr are handled separately.

Impact

Scripts and pipelines that redirect stdout (e.g. command > output.txt)
will have error messages mixed into their output unexpectedly.

Fix

Already submitted in PR #410.

[Caesarsage]

Thank you @namanyadav-08

Resolved by the error-handling refactor (#490/#491): commands return errors up to a single funnel that prints to stderr (cmd/exit.go), keeping stdout clean for command output — which also makes --output json/yaml pipeable.

I believe this can be closed.