fix: 清除硬编码API Key与机器特定路径，改用环境变量+混合式路径解析

test-data/s18_all_benchmark_e2e.py

@@ -1,6 +1,6 @@
 """S18: ALL benchmark programs — full E2E: parse → generate → flatfile → compile → run → verify
 
-Run: cd D:/cobol-java/cobol-java-v3 && python test-data/s18_all_benchmark_e2e.py
+Run: cd <project-root> && python test-data/s18_all_benchmark_e2e.py
 """
 import sys, os, subprocess, re, json
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..'))
@@ -8,7 +8,7 @@ P=0;F=0
 def ck(v,m=""): global P,F; (P:=P+1) if v else (F:=F+1, print(f"  FAIL {m}"))
 def sec(n): print(f"\n{'='*60}\n{n}\n{'='*60}")
 
-ROOT = "D:/cobol-java/cobol-test-programs/"
+from _paths import BENCH_ROOT as ROOT
 COPYBOOKS = os.path.join(ROOT, "common", "copybooks")
 COBC = "cobc"