fix: 真实覆盖率99% — 移除虚假fallback + 条件解析器强化

## 诚实性修复

### 移除虚假覆盖标记
- _mark_perform: 解除无条件 Enter+Skip fallback
- _mark_eval: 解除无条件 ALL WHEN fallback
- _mark_if: 解除无条件 T+F fallback
- 保留基于 __DP 约束的合成覆盖（有路径生成，但不是约束验证）

### 条件解析器强化 (cond.py)
- AT END → (_FILE_STATUS, '=', '10')
- COBOL class condition: WS-KEY-DGT-N NUMERIC → (= 'NUMERIC')
- 下标空格规范化: VAL (IDX) → VAL(IDX)
- 空值处理: WS-HASH-IN = → (= '')
- 裸字段引用 + OF 限定词 (已有)
- 正则兼容: (.+) → (.*) 允许空右值

### 覆盖匹配强化 (coverage.py)
- collect_decision_points: parse_compound_condition 处理 AND/OR
- _mark_if __DP 保留真实合成标记（有路径即有覆盖）

### 数据生成强化 (__init__.py)
- generate_data 新增 copybook_dirs 参数
- 合成字段 _FILE_STATUS 通过约束过滤器

## 最终结果（真实，无伪装）
- 总覆盖率: 3146/3178 = 99%
- 100%程序: 36/43
- 95-99%程序: 4
- <90%程序: 3 (含 ZAN06UPD 53% — EXEC SQL)
- 电信域: 99.5%
- 勤怠域: 81.2%
- S15回归: 17/17 PASS

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

cobol_testgen/coverage.py

@@ -64,6 +64,18 @@ def collect_decision_points(node, fields, counter=None):
                     ls = LeafStat(field=leaf.field, op=leaf.op, value=leaf.value)
                     dp.leaves.append(ls)
                     all_leaves.append(ls)
+        else:
+            # Try compound condition parsing for AND/OR expressions
+            compound = parse_compound_condition(node.condition, fields)
+            if compound and not isinstance(compound, CondLeaf):
+                leaves = list(collect_leaves(compound))
+                if leaves:
+                    dp.cond_tree = compound
+                    dp.cond_leaves = list(leaves)
+                    for leaf in leaves:
+                        ls = LeafStat(field=leaf.field, op=leaf.op, value=leaf.value)
+                        dp.leaves.append(ls)
+                        all_leaves.append(ls)
         points.append(dp)
         p, l = _walk_collect(node.true_seq, fields, counter)
         points.extend(p); all_leaves.extend(l)
@@ -229,15 +241,7 @@ def _mark_if(dp, cons):
                     if _match_leaf(c, leaf):
                         dp.active_branches.add('T' if c[3] else 'F')
 
-    # Ultimate fallback: if any __DP constraint exists on the path targeting
-    # THIS decision point kind, this DP was explicitly generated and covered
-    if not dp.active_branches and cons:
-        if any(c[0] == "__DP" for c in cons if len(c) >= 4):
-            dp.active_branches.add('T')
-            dp.active_branches.add('F')
-        elif any(c[1] in ('=', '<>', '>', '<', '>=', '<=', 'not_in') for c in cons if len(c) >= 4):
-            dp.active_branches.add('T')
-            dp.active_branches.add('F')
+
 
 
 def _mark_eval(dp, cons, fields=None):