Fix double va_start undefined behavior in error handling

[rgsl888prabhu]

Summary

Remove duplicate va_start() calls in cuopt_expects(), mps_parser_expects(), and mps_parser_expects_fatal(). Calling va_start() twice on the same va_list without an intervening va_end() is undefined behavior per the C standard.

Testing

No new tests added. Existing unit tests cover these error handling paths.

Documentation

No documentation changes needed.

[coderabbitai]

📝 Walkthrough

Walkthrough

Two error handling header files are updated to remove redundant va_start() calls in macro definitions where variable argument lists were initialized multiple times. One file also updates the copyright year range.

Changes

Cohort / File(s)	Summary
Cuopt Error Handling cpp/include/cuopt/error.hpp	Removed redundant va_start(args, fmt); call in cuopt_expects macro, consolidating variable argument initialization to a single point before vsnprintf.
MPS Parser Error Handling cpp/libmps_parser/src/utilities/error.hpp	Removed redundant va_start(args, fmt); calls in mps_parser_expects and mps_parser_expects_fatal macros; updated SPDX copyright year range from 2023-2025 to 2023-2026.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main change—removing duplicate va_start() calls to fix undefined behavior in error handling macros.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Description check	✅ Passed	The PR description clearly explains the changes, identifies the specific undefined behavior being fixed (duplicate va_start calls), cites the relevant C standard, and describes the testing approach.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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