DOC: add latest eval leaderboard (bm25/vector/hybrid)

Author: fahadamjad009

reports/eval_leaderboard_latest.csv

@@ -0,0 +1,4 @@
+file,mode,recall@1,recall@3,recall@5,recall@10,mrr@10,ndcg@10
+eval_report_bm25_20260208_150305.json,bm25,0.2,0.5,0.6,0.7,0.5666666666666667,0.5191245504312427
+eval_report_hybrid_rrf_20260208_150320.json,hybrid_rrf,0.3,0.6,1.0,1.0,0.5900000000000001,0.7002531670683775
+eval_report_vector_20260208_150703.json,vector,0.2,0.6,0.7,0.8,0.5000000000000001,0.5512362347719677