Runner: run_solver.py update with xpress

[finozzifa]

The goal of this pull request is add support for the xpress solver in the run_solver.py script.

run_solver.py

The applied changes are:

• def get_solver: I have added the seed_options for xpress, based on this documentation page and this documentation page.
• def def is_mip_problem: I have added an if branch for xpress to understand whether a given solver model is a MIP problem. I based this change on this documentation page and this documentation page.
• def get_reported_runtime: I have added an if branch for xpress to get the solver runtime. I based this change on this documentation page and this documentation page.
• def get_duality_gap: I have added an if branch for xpress. The change is based on this documentation page and this documentation page (for how to accessing controls).

Test

I tested the changes to run_solver.py on the benchmark pypsa-eur-elec-trex-3-12h.lp.

I get:
{"runtime": 1.298514694000005, "reported_runtime": 0.93, "status": "ok", "condition": "optimal", "objective": 7398190482.723573}

The value of the objective function is compatible to those found here

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Project	Deployment	Actions	Updated (UTC)
solver-benchmark	Ready	Preview, Comment	Feb 11, 2026 4:38pm

[Vamsipriya22]

This PR looks good overall 👍

However, the CI check is currently failing due to a URL validation error. That issue appears to already be addressed in PR #417.

I suggest merging PR #417 first; once that is in, the failing check here should disappear and this PR can be merged cleanly.