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/23-select-condition/README.md

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+# 23-select-condition — SELECT Condition Simulation
+
+## 电信业务场景
+
+客户合同检索。使用索引文件模拟SELECT条件检索，通过START+READ NEXT实现条件匹配和范围查询。
+
+## Purpose
+Simulates SQL SELECT with WHERE conditions using GnuCOBOL INDEXED files and START/READ NEXT operations.
+
+## Test Coverage
+1. **Single record by key** — READ with KEY IS (exact match WHERE)
+2. **Range query** — START with NOT LESS THAN, loop with upper bound check
+3. **Zero results** — Key not found, INVALID KEY handling
+4. **Greater-than query** — START with GREATER THAN, read all following records
+
+## Key Techniques
+- INDEXED file ORGANIZATION with DYNAMIC access
+- START for positioning (KEY IS GREATER THAN / NOT LESS THAN)
+- READ NEXT for sequential traversal
+- FILE STATUS checking
+- INVALID KEY / NOT INVALID KEY for conditional handling