parquet_tables_query Submodule

Introspection and name resolution for parquet_table: the row/column counts, the per-column queries (%kind, %width, %unit, %residency, %is_null), and the shared lookup and guard helpers every value accessor is built on.

Two conventions run through the whole file:

• The lookup key is always the column's INTERNAL name, never the physical name in the file. They are the same today; keeping every lookup in table_find is what will let a read-time remap change that in one place.
• found= decides whether a miss is fatal. Absent, a missing column is a hard error stop; present, the miss is reported through it and the call returns quietly.