fix: remove hard-coded absolute paths from evaluator

[AaryanCode69]

Summary

Remove hard-coded absolute paths from the evaluation script and make them configurable via CLI arguments, with automatic fallback to the project's existing EmbeddingEnvironment resolver.

Problem

src/evaluation/evaluator.py contained two hard-coded absolute paths pointing to a specific developer's local machine:

# Line 74 — CSV path for BM25 retrieval
loader = CSVLoader(
    "/Users/hmohammadi/Desktop/react_to_me_github/reactome_chatbot/embeddings/.../summations.csv"
)

# Line 182 — ChromaDB embeddings directory
embeddings_directory = "/Users/hmohammadi/Desktop/react_to_me_github/reactome_chatbot/embeddings/.../summations"

This made it impossible to:

• Run the evaluator on any other machine
• Use it in CI/CD pipelines
• Containerize the evaluation workflow with Docker

Solution

Replace the hard-coded paths with two new CLI arguments that integrate with the project's existing EmbeddingEnvironment utility:

# Zero-config: auto-resolves from embeddings/current
python evaluator.py --testset_dir ./example --rag_type advanced

# Explicit override when needed
python evaluator.py --testset_dir ./example --rag_type advanced \
  --embeddings_dir ./embeddings/openai/text-embedding-3-large/reactome/Release90/summations \
  --csv_path ./embeddings/openai/text-embedding-3-large/reactome/csv_files/summations.csv

Path Resolution Logic

--embeddings_dir provided?
  ├── Yes → use it directly
  └── No  → EmbeddingEnvironment.get_dir("reactome") / "summations"

--csv_path provided?
  ├── Yes → use it directly
  └── No  → <parent of embeddings_dir> / "csv_files" / "summations.csv"

Both paths validated for existence before proceeding.

Changes

File	Change
src/evaluation/evaluator.py	Removed 2 hard-coded absolute paths; added --embeddings_dir and --csv_path CLI args; added _resolve_paths() helper with EmbeddingEnvironment fallback and existence validation; updated initialize_rag_chain_with_memory() signature to accept csv_path

Design Decisions

• CLI arguments over environment variables — consistent with the script's existing argparse interface (--testset_dir, --model, --rag_type) and the companion test_generator.py which also uses argparse.
• Fallback to EmbeddingEnvironment — reuses the project's existing path resolution utility (src/util/embedding_environment.py) rather than inventing a new mechanism. This is the same resolver used by the main application at runtime.
• Both args optional — enables zero-config usage for developers who have already run embeddings_manager use, while CI and Docker can pass explicit paths.
• Existence validation — _resolve_paths() raises FileNotFoundError with a clear message before any expensive initialization runs.

Backward Compatibility

• All existing CLI arguments remain unchanged.
• The script runs identically to before when explicit --embeddings_dir and --csv_path are provided matching the old hard-coded values.
• No changes to any other files in the repository.

Related Issue

Resolves #109