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/25-subprogram/README.md

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+# 25-subprogram
+
+## 电信业务场景
+
+计费子程序。通过CALL语句调用计费计算子程序，传入用量和单价参数，返回计费金额。演示USING参数传递和RETURN-CODE使用。
+
+## Purpose
+Tests COBOL subprogram calling conventions including CALL with literal names,
+CALL with variable program names, and CALL with IS INITIAL.
+
+## Architecture
+- **callee.cbl** — Subprogram (PROGRAM-ID. callee) that adds two numbers via
+  LINKAGE SECTION parameters and tracks first-call state.
+- **caller.cbl** — Main program (PROGRAM-ID. caller) with three test cases.
+
+## Tests
+1. **CALL literal**: CALL "callee" USING 100 200 -> expects 300
+2. **CALL variable**: CALL WS-PGM-NAME USING 10 20 -> expects 30
+3. **CALL IS INITIAL**: CALL "callee" IS INITIAL USING 1 2 -> expects 3,
+   forces subprogram reinitialization
+
+## Key Techniques
+- CALL USING for parameter passing
+- LINKAGE SECTION for parameter definitions
+- GOBACK to return to caller
+- RETURN-CODE for status communication
+- IS INITIAL to reinitialize subprogram state