_compute_infeasibilities_xpress returning wrong set of constraints

[luciana-marques]

Version Checks (indicate both or one)

• I have confirmed this bug exists on the lastest release of Linopy.

• I have confirmed this bug exists on the current master branch of Linopy.

Issue Description

linopy._compute_infeasibilities_xpress uses enumerate(solver_model.getConstraint()) to create a position-to-constraint mapping, then returns those positions as "linopy labels." But the LP only contains non-masked rows (labels 0, 2, 4... skipping -1), so Xpress row position 1 = LP row "c2" = linopy label 2, not position 1. find_single(1) then maps to the wrong generator coordinate (e.g., 'b' instead of 'c').

Reproducible Example

(I will skip this, because I generated the bug using confidential data)

Expected Behavior

An IIS with a set of constraints that are not even part of the model

Installed Versions

Details

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