fix(rest): reject blob offsets on non-Puffin delete files

[fallintoplace]

What changed

Reject content-offset and content-size-in-bytes on position-delete files unless the file format is Puffin.

Why

These fields locate a deletion-vector blob inside a Puffin file. The decoder required them for Puffin files but accepted them on Parquet, Avro, and ORC position-delete files, creating an inconsistent DataFile.

Testing

• Added cases for offset only, size only, and both fields on a non-Puffin position-delete file
• Existing Puffin and equality-delete validation remains covered
• go test ./catalog/rest