fix: ruff lint fixes for v3 test files

tests/test_pbt_v3_clustering.py

@@ -10,18 +10,13 @@ Validates: Requirements 4.2, 4.3, 4.4, 4.5, 21.4
 """
 from __future__ import annotations
 
-import math
-
 from hypothesis import given, settings
 from hypothesis import strategies as st
 
 from services.aggregation.worker import (
-    EvidenceCluster,
-    cluster_evidence,
     compute_cluster_llr,
     compute_n_eff,
 )
-from services.aggregation.scoring import EvidenceUnit
 
 # ---------------------------------------------------------------------------
 # Hypothesis strategies