Report Generation: Adding unit tests

[lotif]

Summary

Adding unit tests for the report generation modules.

Also:

• Removing langfuse project name variable (not needed given the langfuse key is already associated with the project)
• Fixing some minor bugs that were found while writing the tests.
• Updating pypdf v6.6.2 -> v6.7.2 to solve security issue (https://github.com/VectorInstitute/eval-agents/actions/runs/22316523156/job/64562889561?pr=64)

Clickup Ticket(s): NA

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
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test improvements
• 🔒 Security fix

Changes Made

Adding unit tests for the report generation modules.
Removing langfuse project name variable (not needed given the langfuse key is already associated with the project).
Fixing some minor bugs that were found while writing the tests.
Updating pypdf v6.6.2 -> v6.7.2 to solve security issue (https://github.com/VectorInstitute/eval-agents/actions/runs/22316523156/job/64562889561?pr=64).

Testing

• Tests pass locally (uv run pytest tests/)
• Type checking passes (uv run mypy <src_dir>)
• Linting passes (uv run ruff check src_dir/)
• Manual testing performed (describe below)

Checklist

• Code follows the project's style guidelines
• Self-review of code completed
• Documentation updated (if applicable)
• No sensitive information (API keys, credentials) exposed