Pad-model extension assumed OPM-style "Z+" for the positive-Z exterior face,
but ResInsight emits "Z" (OPM-Flow short form). The K1/K2 shift never fired,
leaving the bottom boundary face at the original NZ instead of the new
padded NZ. Match both "Z" and "Z+" so the extension applies.
Adds a regression test verifying that with BCCON_BCPROP and padding the "Z"
exterior face is shifted by nzUpper + nzLower while the "Z-" face remains
at K=1, and documents the exterior-face semantics of the direction mapping.
Only prepend/append padding rows to RSVD/RVVD/RTEMPVD/PBVD/PDVD tables
when the existing table does not already cover the padding depth range.
This prevents non-monotonic depth sequences that caused issues in OPM.
Also expose extendDepthTable as a public static method on RigPadModel
and add unit tests for all extension scenarios.
Co-authored-by: Vegard Kippe <vkip@equinor.com>
Kristian Bendiksen
