Sector-aware macro feature selection pipeline

[v-atharva]

Summary

• replace feature-selection analysis with per-ticker lagged Spearman + sector-prior scoring
• add sector classification config and sector-prior rules module
• update CLI with --top-k and new output artifacts
• add unit + integration tests for ranking logic, priors, and pipeline outputs
• update .gitignore with relative data directory rules

Validation

• python -m pytest tests/unit/test_feature_selection.py tests/integration/test_feature_selection_pipeline.py