Allow debug files in unmet demand scenario

[tsmbland]

Description

Slightly reworking things so that we can get debug output files in scenarios with unmet demand

Fixes #1083

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc
• Update release notes for the latest release if this PR adds a new feature or fixes a bug
  present in the previous release

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

❌ Patch coverage is 18.75000% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.31%. Comparing base (25f3813) to head (090fa41).

Files with missing lines	Patch %	Lines
src/simulation/optimisation.rs	18.75%	12 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1085      +/-   ##
==========================================
+ Coverage   82.26%   82.31%   +0.05%     
==========================================
  Files          53       53              
  Lines        7416     7409       -7     
  Branches     7416     7409       -7     
==========================================
- Hits         6101     6099       -2     
+ Misses       1025     1021       -4     
+ Partials      290      289       -1     

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[Copilot]

Pull request overview

This PR enables debug file output for scenarios where dispatch optimization fails due to unmet demand. Previously, when the solver encountered an infeasible model, it would re-run with unmet demand variables to identify problematic markets but would not write debug CSV files. Now, debug information is written for both successful runs and infeasible scenarios before returning an error.

Changes:

• Modified the run method signature from consuming self to borrowing &self
• Ensured debug info is written in both success and infeasible cases
• Inlined the get_markets_with_unmet_demand helper function into the main error handling path

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[alexdewar]

I think we should panic if the optimisation run with unmet demand variables fails, but other than that, LGTM!

[alexdewar]

I actually think this should stay as an expect(), because this optimisation should be the same as the last one, but with unmet demand variables, so if we get an error here something has gone badly wrong.