🔧 Fix JSONL Output Instructions in Workflow Templates

[dsyme]

Summary

• Updated workflow template instructions to emphasize correct JSONL output
• Clarified guidance on appending entries and validating JSONL files
• Added explicit warning about incorrect line separation in JSONL entries

Key Changes

• Modified instructions to use "Append an entry on a new line" instead of "Write an entry"
• Added explicit guidance about reading back and validating JSONL entries
• Included a specific warning about incorrectly separating entries with "\n"

Context

These changes improve the clarity of instructions for safely writing output files in GitHub workflow templates, reducing the potential for errors in JSON line formatting.