🧹 Refactor: Extract listModelFiles function into a shared utility module

[akutuva21]

🎯 What: Extracted the duplicated listModelFiles function from scripts/generate-manifest.js and scripts/validate-metadata.js into a shared utility module (scripts/utils.js).
💡 Why: To improve code maintainability and adhere to DRY principles by removing duplicated code.
✅ Verification: Ran node --test to ensure tests passed. Executed node scripts/generate-manifest.js and node scripts/validate-metadata.js to confirm both scripts continue to work correctly after the refactoring.
✨ Result: Code duplication is eliminated and the scripts successfully utilize the shared module without loss of functionality.

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PR created automatically by Jules for task 7277451205665425511 started by @akutuva21

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[akutuva21]

Reviewed in sequence. listModelFiles extraction to scripts/utils.js is clean and behavior-preserving.