fix: 修复 trigger.operator null + 添加覆盖反馈重试 - Closes #22, Closes #21

#22: _normalize_rule 补充 trigger 级别 operator (AND/OR) 默认值
#21: step1 验证失败时自动生成覆盖反馈并重试一轮
#22: step2 过滤空规则片段，避免污染下游

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

skills/ir_generation_skill/step3_merge_and_audit.py

@@ -139,6 +139,10 @@ def _normalize_rule(rule: dict) -> dict:
 
     trigger = rule["trigger"]
 
+    # Ensure trigger-level combining operator (AND/OR) for multi-condition triggers
+    if not trigger.get("operator"):
+        trigger["operator"] = "AND"
+
     # If trigger has an event, it's event-based (no conditions needed)
     if trigger.get("event") is not None:
         return rule
@@ -147,7 +151,7 @@ def _normalize_rule(rule: dict) -> dict:
     if "conditions" not in trigger:
         trigger["conditions"] = []
 
-    # Fix null operators in conditions
+    # Fix null operators in individual conditions
     for cond in trigger["conditions"]:
         if not cond.get("operator"):
             cond["operator"] = "=="
@@ -158,7 +162,6 @@ def _normalize_rule(rule: dict) -> dict:
 
     # If still no conditions, add a default one
     if not trigger["conditions"]:
-        trigger["operator"] = "AND"
         trigger["conditions"] = [{
             "signal": "system_state",
             "operator": "==",