Prevent conflicting repos to be added via mlc add repo

[amd-arsuresh]

✅ PR Checklist

• Target branch is dev

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

✅ Testing & CI

• Have tested the changes in my local environment, else have properly conveyed in the PR description
• The change includes a GitHub Action to test the script(if it is possible to be added).
• No existing GitHub Actions are failing because of this change.

📚 Documentation

• README or help docs are updated for new features or changes.
• CLI help messages are meaningful and complete.

📁 File Hygiene & Output Handling

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

🛡️ Safety & Security

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

🙌 Contribution Hygiene

• PR title and description are concise and clearly state the purpose of the change.
• Related issues (if any) are properly referenced using Fixes # or Closes #.
• All reviewer feedback has been addressed.

[github-actions]

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