Hand-written submodule of parquet_maml_base (NOT generated). Implements the parquet_maml_file%add_col_qc and %set_col_qc (both subroutines) type-bound procedures, whose deferred module-procedure interfaces are declared in the (generated) src/parquet_maml_base.f90. Both share one worker (add_col_qc_impl) and differ only in how the parsed column name is returned: add_col_qc via an optional out-argument, set_col_qc via its own intent(inout) argument (so a caller can reuse one variable in place, which add_col_qc's two-argument form cannot do due to intent(out)/intent(in) aliasing).
add_col_qc/set_col_qc build a read-time qc-maml incrementally from a compact one-line "col, min, max, miss" string, appending a fields: entry with a qc: block. It is deliberately self-contained (only intrinsic string handling): its parent module sits at the bottom of the module stack, so it cannot reuse the qc-maml validation helpers in parquet_metadata without creating a dependency cycle. The operator-direction and miss-value rules it enforces mirror those in parquet_metadata's parquet_parse_qc_maml / parquet_validate_maml_internal.