Fix simulator logs containing future messages

[cemde]

Description

MessageHistory.to_list() returned a direct reference to the internal _messages list. This caused simulator log entries to be mutated after creation. Each entry's conversation_history ended up containing messages from future turns that hadn't occurred at logging time. Fixed by returning a shallow copy.

Fixes #5

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code quality improvement (refactoring, formatting, etc.)

Checklist

Contribution

• I have read the CONTRIBUTING.md guide.
• Commits follow "How to write a good git commit message"

Documentation

• Added/updated docstrings for new/modified functions as instructed CONTRIBUTING.md
• Updated relevant documentation in docs/ (if applicable)
• Tag github issue with this PR (if applicable)

Changelog

• Added entry to CHANGELOG.md under [Unreleased] section
  • Use Added section for new features
  • Use Changed section for modifications to existing functionality
  • Use Fixed section for bug fixes
  • Use Removed section for deprecated/removed features
• OR this is a documentation-only change (no changelog needed)

Architecture (if applicable)

• Core/Interface separation: Changes in maseval/core/ do NOT import from maseval/interface/
• Dependencies: New core dependencies added sparingly; framework integrations go to optional dependencies

Additional Notes

None.

[github-actions]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
maseval/core
history.py
Project Total

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