fix(frontmatter): improve duplicate frontmatter key error handling

[codeafridi]

Summary

I fixed an issue with YAML frontmatter where duplicate keys caused a vague error that didn’t point to the real problem. I added a simple check that detects repeated keys and shows a clear message with the key name and line number which points to the file

Test plan

-ensured normal frontmatter files still parse correctly. -ran the formatter manually to confirm it now identifies the duplicated key. -verified that the error message displays the correct key and the line where it occurs.

Checklist

Please add a x inside each checkbox:

• [ x ] I have read the contribution guidelines.

[codeafridi]

Thanks for the feedback. ill update it now.

• i will remove the thrown error and replace it with a simple console.log warn without a stack trace.
• i will include the file path, key name, and line number in the warning message so it’s clear which entry is affected. -then limit the detection to the currently opened entry, so warnings don’t appear for every file in the collection.
• yes cms users shouldn’t see this so i will keep it in the console only for developers.

I’ll push the changes soon.

[codeafridi]

Alright now I get it. I'll now

-parse yaml structure properly -track full key paths -only warn when the same key appears in the same parent scope -ennsuring all existing tests pass before pushing the update

[codeafridi]

do tell if any changes are needed.