develop: 补齐根因分析 RootCauseAnalyzer 实现与单元测试（132 tests OK）

tests/test_root_cause.py

@@ -59,7 +59,6 @@ class TestRootCauseAnalyzer(unittest.TestCase):
         )
         rc = self.analyzer.analyze(_log("No space left on device"), [event])
         self.assertEqual(rc.cause_type, "disk_full")
-        # 0.6（日志） + 0.25（指标） + 0.15（互相印证） = 1.0
         self.assertEqual(rc.confidence, 1.0)
         self.assertTrue(any(e["type"] == "event" and e["event_id"] == "e-1" for e in rc.evidence))
 
@@ -90,7 +89,7 @@ class TestRootCauseAnalyzer(unittest.TestCase):
         rc = self.analyzer.analyze(_log("No space left on device"), [outside])
         self.assertEqual(rc.cause_type, "disk_full")
         self.assertEqual(rc.confidence, 0.6)
-        self.assertEqual(len(rc.evidence), 1)  # 仅日志证据，无事件证据
+        self.assertEqual(len(rc.evidence), 1)
 
     def test_host_mismatch_excluded(self):
         event = Event(