fix(table): reject ambiguous equality-delete columns

[fallintoplace]

What changed

Reject equality-delete files when a field ID resolves to a column name that occurs more than once in the physical Arrow schema.

Why

Arrow permits duplicate field names. The reader previously selected the first match, which could apply deletion semantics using an arbitrary physical column while silently ignoring another column with the same name.

Testing

• Added an end-to-end scan using a Parquet equality-delete file with duplicate id columns and different values
• go test ./table