Add GPT-OSS model download script

[anandhu-eng]

🧾 PR Checklist

• Target branch is dev

📌 Note: PRs must be raised against dev. Do not commit directly to main.

📁 File Hygiene & Output Handling

• No unintended files (e.g., logs, cache, temp files, pycache, output folders) are committed

📝 Comments & Communication

• Proper inline comments are added to explain important or non-obvious changes
• PR title and description clearly state what the PR does and why
• Related issues (if any) are properly referenced (Fixes #, Related to #, etc.)

🛡️ Safety & Security

• No secrets or credentials are committed
• Paths, shell commands, and environment handling are safe and portable

[github-actions]

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