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## Description
<!-- Provide a clear description of the changes in this PR -->
• Created DirectLLMEvalAdapter - a lightweight alternative to DeepEval
for answer evaluation
• Added evaluation prompt files defining scoring criteria and format
• Made adapter selectable via evaluation_engine = "DirectLLM" in config,
supports "correctness" metric only
## DCO Affirmation
I affirm that all code in every commit of this pull request conforms to
the terms of the Topoteretes Developer Certificate of Origin
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## Summary by CodeRabbit
- **New Features**
- Introduced a new evaluation method that compares model responses
against a reference answer using structured prompt templates. This
approach enables automated scoring (ranging from 0 to 1) along with
brief justifications.
- **Enhancements**
- Updated the configuration to clearly distinguish between evaluation
options, providing end-users with a more transparent and reliable
assessment process.
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