Possible problem on `contype=L`; verify these problems against SIF

The classification tests compare `contype=L` against decoding and counting the linear constraints.
- SIF says these problems have linear constraints, but deconding gives otherwise:
"RDW2D52U", "RDW2D52F", "RDW2D52B", "RDW2D51U", "RDW2D51F"
- Decoding gives linear constraints, but SIF disagrees:
"STEENBRA", "DALLASM", "GRIDNETC", "GRIDNETH", "GRIDNETG", "STEENBRD", "BIGBANK", "GRIDNETI", "LINSPANH", "STEENBRE", "SPANHYD", "GRIDNETE", "GRIDNETF", "STEENBRF", "GRIDNETD", "SMBANK", "LSNNODOC", "DALLASS", "GRIDNETA", "STEENBRG", "GRIDNETB", "STEENBRC", "DALLASL", "WATER", "STEENBRB"

Start by examining the classification tests and the SIF, decoding, and linear-constraint counting paths for the listed problems. Compare both groups systematically and document whether each reported discrepancy is a real classification bug or an expected difference; done means the mismatches are explained and the required test or issue updates are identified.

Written by the indexing model from the issue text.