feat: add benchmark-programs — 58 telecom COBOL test programs

作为子目录纳入系统，与核心测试管道协同

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

benchmark-programs/05-branch-if/README.md

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+# 05-branch-if — IF Branch Program
+
+## 电信业务场景
+
+料金阶梯判定。根据通话时长进行IF条件分支，将用量分为低额/中额/高额三个料金段，分别写入不同输出文件。
+
+Demonstrates GnuCOBOL IF branching patterns:
+
+- **IF 2-way (ELSE)**: Test DATA1 prefix for "SPECIAL"
+- **IF 3-way (ELSE IF)**: Branch DATA2 value to three output files
+- **Compound AND/OR**: Combine multiple conditions in one IF
+- **88-level condition name**: Implicit condition test on KEY field
+- **IF nested 3 levels**: Nested IF checks on DATA2 and KEY
+
+## Files
+
+| File | Purpose |
+|------|---------|
+| `main-05-branch-if.cbl` | COBOL program (fixed format) |
+| `data-gen.sh` | Generate 12-records FILE-IN.DAT |
+| `run.sh` | Compile, run, verify outputs |
+
+## Input Record
+
+| Field | Type | Length |
+|-------|------|--------|
+| KEY | PIC X | 10 |
+| DATA1 | PIC X | 20 |
+| DATA2 | PIC 9 | 10 |
+
+## Branch Logic
+
+| Condition | Output File |
+|-----------|-------------|
+| DATA2 < 1000 | FILE-OUT-A.DAT |
+| DATA2 >= 1000 AND <= 5000 | FILE-OUT-B.DAT |
+| DATA2 > 5000 | FILE-OUT-C.DAT |