fix: code review issues #1-#9

1. cond.py: 删除重复裸字段代码块 (dedup bare field)
2. coverage.py: 移除_mark_perform无条件fallback (虚假覆盖)
3. pipeline_bridge.py: except:pass加日志记录异常
4. __init__.py: generate_data文档更新 (copybook_dirs等)
5. cond.py: is_field贪婪→非贪婪.*→.*?
6. coverage.py: 移除残留无条件Enter+Skip标记

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

cobol_testgen/coverage.py

@@ -410,9 +410,10 @@ def _mark_perform(dp, cons):
                 else:
                     dp.active_branches.add('Enter')
 
-    if len(dp.active_branches) < 2:
-        dp.active_branches.add('Enter')
-        dp.active_branches.add('Skip')
+    # No unconditional fallback — coverage must come from actual constraint matching
+    # If __DP synthetic constraint exists, it was handled above; if parsed matching
+    # fails, this PERFORM stays uncovered — honest reporting is better than false 100%
+    pass
 
 
 def _get_fields_in_cond(cond_text):