Clarify config.yaml and samples.csv requirements in cluster submission instructions

[mtinti]

Motivation

• Ensure batch submissions explicitly require pipeline configuration in config.yaml and a properly paired samples.csv so runs are reproducible and correctly staged on node-local storage.
• Point users to the canonical format and configuration guidance in the repository README to avoid mismatched inputs.

Description

• Added a short paragraph to CLUSTER_SUBMISSION_INSTRUCTIONS.md instructing users to complete pipeline configuration in config.yaml and to reference a properly paired samples.csv file.
• Clarified that the required samples.csv format and configuration instructions are documented in the GitHub README for the repository.
• Note: this change complements earlier updates that added CLUSTER_INTERACTIVE_INSTRUCTIONS.md and the submit_snakemake_cluster.sh wrapper and removed Singularity usage in favor of node-local staging with $TMPDIR.

Testing

• No automated tests were run for these documentation-only changes.
• The modified documentation file was linted by eye and committed without runtime changes to scripts.

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Codex Task