fix: 存根任务三个根本问题修复

1. gap_detector: TypeError/takes no arguments也识别为stub_returns_none
   （之前只匹配assert None==和NoneType，漏掉了TypeError模式）
2. generator: 逐函数patch全失败时fallback到whole_file路径
   （之前返回None导致patches=0）
3. generator: codegen路径文件已存在时走whole_file覆盖
   （之前生成pipeline_1.py，测试跑的还是原文件）

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kaiwu/core/gap_detector.py

@@ -134,6 +134,13 @@ class GapDetector:
         none_calls = len(re.findall(r'where None = \w+\(', output))
         if none_calls >= 2:
             return True
+        # 扩展模式：TypeError: XxxClass() takes no arguments（pass的__init__被调用）
+        if 'TypeError' in output and 'takes no arguments' in output:
+            return True
+        # 扩展模式：多个TypeError（存根类被实例化/调用）
+        type_errors = len(re.findall(r'TypeError:', output))
+        if type_errors >= 3:
+            return True
         return False
 
     def _all_passed(self, output: str) -> bool:

kaiwu/experts/generator.py

@@ -297,8 +297,9 @@ class GeneratorExpert:
                 explanation_parts.append(f"{fpath}:{func_name}")
 
         if not patches:
-            logger.warning("Generator: no patches produced")
-            return None
+            # Fallback: 逐函数patch全失败时，尝试whole_file路径
+            logger.warning("Generator: no patches produced, trying whole_file fallback")
+            return self._run_whole_file(ctx, files)
 
         result = {
             "patches": patches,
@@ -570,15 +571,14 @@ class GeneratorExpert:
         import os
         full_path = os.path.join(ctx.project_root, target_file)
 
-        # 防止覆盖已有文件：如果文件已存在，加数字后缀
+        # 如果文件已存在，走whole_file覆盖（不生成_1.py）
         if os.path.exists(full_path):
-            base, ext = os.path.splitext(target_file)
-            for i in range(1, 100):
-                candidate = f"{base}_{i}{ext}"
-                if not os.path.exists(os.path.join(ctx.project_root, candidate)):
-                    target_file = candidate
-                    full_path = os.path.join(ctx.project_root, candidate)
-                    break
+            result = {
+                "patches": [{"file": target_file, "content": code, "write_mode": "whole_file"}],
+                "explanation": f"已覆盖：{target_file}",
+            }
+            ctx.generator_output = result
+            return result
 
         result = {
             "patches": [{"file": target_file, "original": "", "modified": code}],