fix: Silent network optimization failure

[pkroening]

Closes #2255.

Changes proposed in this Pull Request

1. Check "warning" against status instead of condition
2. Move warning check below infeasibility check, since infeasibility conditions come with a warning status
3. Rewrite checks with linopy constants to add indirect context
4. Add entry to release_notes.md

Checklist

Required:

• Changes are tested locally and behave as expected.
• Code and workflow changes are documented.
• A release note entry is added to doc/release_notes.md.
• The description is human-written and any AI-generated content is marked.

[Copilot]

Pull request overview

Fixes a silent failure mode in scripts/solve_network.py by ensuring solver warnings are detected correctly (using solver status, not termination condition) and reported as hard errors, preventing export of unsolved networks.

Changes:

• Use linopy.constants (SolverStatus, TerminationCondition) for clearer, more explicit status/termination checks.
• Check infeasibility conditions before handling warning status (since infeasibility may also come with warning status).
• Add a release note entry documenting the new error behavior for warning status.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
scripts/solve_network.py	Updates solver result validation logic to raise on warning status and to detect infeasibility via explicit termination-condition constants.
doc/release_notes.md	Documents the behavioral change (raise error when solver status is warning).

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[pkroening]

I want to add that this PR was created without AI. This is my first PR and I was not aware that Copilot reviews by default. I have now opted out. :)

[fneum]

Excellent! Thank you very much!