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/cross-cutting/date/README.md

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+# Date Processing
+
+## Test Cases
+
+| Test ID | Description |
+|---------|-------------|
+| D-N001 | YYYYMMDD basic processing (parse year/month/day) |
+| D-N002 | Leap year detection (2000=leap, 2100=no, 2024=leap, 2025=no) |
+| D-N003 | Month-end days (Jan 31, Feb 28/29) |
+| D-N004 | Date comparison (<, >, =) |
+| D-A001 | FUNCTION INTEGER-OF-DATE date arithmetic (21 day diff) |
+| D-A002 | Date arithmetic with FUNCTION DATE-OF-INTEGER |
+| D-A003 | Invalid dates (Feb 30, Apr 31) |
+| D-A004 | 2-digit year (YYMMDD) ambiguity |
+| D-W001 | Japanese era: Reiwa R010501 = 2019/05/01 |
+| D-W002 | Japanese era: Heisei H010108 = 1989/01/08 |
+| D-W003 | Reiwa 6 (R060101 = 2024/01/01) |
+| D-W004 | Showa era (S640101 = 1989/01/01) |
+| D-W005 | Format conversion YYYYMMDD to YYMMDD |
+| D-W006 | YYYYMMDD to Wareki string |
+| D-W007 | Cross-era date comparison |
+| D-F001 | FUNCTION CURRENT-DATE |
+| D-F002 | Century boundary handling |
+| D-F003 | Julian date format |
+
+## Features Covered
+- YYYYMMDD and YYMMDD processing
+- Leap year rules (divisible by 400 vs 100)
+- Month-end calculation
+- FUNCTION INTEGER-OF-DATE / DATE-OF-INTEGER for arithmetic
+- Date comparison operators
+- Invalid date storage
+- Japanese era (Wareki) representation: Reiwa/Heisei/Showa
+- Format conversion between date representations
+
+## Expected Results
+All 18 tests should display PASS.