fix: resolve 3 MEDIUM code review findings

M1: Cache confusion-pair confidences in Path B (eliminate redundant
    resolve_confusion_pair re-calls in _path_rule_engine)
M2: Resolve contradictions in Path C instead of hardcoding
    resolved_count=0 in _path_llm_assisted
M4: Add DIVIDE_25 to contradiction pair coverage (50-25, 100-25)
    and update test_contradiction_pairs_defined to verify all 3 variants

hina/rule_engine/contradiction.py

@@ -45,6 +45,16 @@ CONTRADICTION_PAIRS: list[dict[str, str]] = [
         "type_a": "DIVIDE_50",
         "type_b": "DIVIDE_100",
     },
+    {
+        "name": "division_50_25_100",
+        "type_a": "DIVIDE_50",
+        "type_b": "DIVIDE_25",
+    },
+    {
+        "name": "division_50_25_100",
+        "type_a": "DIVIDE_100",
+        "type_b": "DIVIDE_25",
+    },
     {
         "name": "mn_output_mode",
         "type_a": "M:N",