fix: gcov Windows本地化 + runner合并 + 决策覆盖率修复

- gcov从WSL 15.2改为Windows MinGW 9.2.0，消除.gcno格式不匹配
- coverage.py去除leaf_stats复位bug（决策覆盖率恢复）
- runner.py合并V3编译+SOURCE分组执行+出力保存
- __init__.py gcov条件/outdir解析修复

cobol_testgen/__init__.py

@@ -288,6 +288,9 @@ def main():
     if '--gcov' in args:
         gcov_mode = True
         args.remove('--gcov')
+        if not _HAVE_RUNNER:
+            logger.warning("--gcov: runner.py not found. Compile/run will be skipped. "
+                           "Use --gcov without runner only generates test data + static coverage.")
     i = 0
     while i < len(args):
         if args[i] == '--temp-dir':
@@ -309,7 +312,7 @@ def main():
     outdir = None
     for a in args:
         p = Path(a)
-        if p.is_dir():
+        if p.is_dir() or (not p.suffix and p.parent.exists()):
             outdir = p
         elif p.suffix.upper() in ('.CBL', '.COB', '.CPY'):
             cobol_files.append(p)
@@ -553,7 +556,7 @@ def main():
                            data_fields=fields_dict, select_info=select_info)
 
         gcov_data = None
-        if gcov_mode and proc_div and _HAVE_GCOV:
+        if gcov_mode and proc_div and _HAVE_GCOV and _HAVE_RUNNER:
             _temp = temp_dir or str(outdir / '.gcov_cache')
             source_dir = str(filepath.parent)
             expected_records: list[dict] = [{}] * len(records)