fix(wrapper): stop reporting success after failed dry-runs #151

Summary

When dryrun() pipes Snakemake output through tee, the wrapper prints OK Dry-run completed. even if Snakemake exits non-zero. The dry-run path should capture the pipeline exit status and only report success when the dry-run actually succeeds.

Acceptance Criteria

• Failed Snakemake dry-runs do not print a success message.
• The wrapper exits non-zero when the dry-run fails.
• The change is validated with a failing dry-run case.

Parent issue: #127

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