Validate upstream workflow starters

[ehsanestaji]

Summary

• Align the nf-core starter with current nf-core module metadata, topic-version output, conda/container conventions, and evidence-preserving exit-code handling.
• Reshape the Snakemake wrapper starter to upstream layout with root wrapper.py, Linux pin txt, logs, captured exit_code output, and upstream pytest snippet.
• Document the completed upstream-style validation results and update adoption/readiness next steps.

Validation

• python3 -m unittest discover -s tests/python
• cargo test --locked
• nf-core modules lint fastaguard: 47 passed, 0 warnings, 0 failures
• nf-core modules test fastaguard --profile conda --once --no-prompts: all tests passed
• Snakemake upstream checks: black --check, snakefmt --check, snakemake --lint, pytest test_wrappers.py::test_fastaguard

Notes

This keeps FastaGuard positioned as a FASTA preflight layer and prepares external upstream PRs without claiming official nf-core or Snakemake acceptance yet.