feat: complete INSPECT/SEARCH support, fix PERFORM/EVAL coverage marking

- Add INSPECT (TALLYING/REPLACING/CONVERTING) with BEFORE/AFTER INITIAL
- Add SEARCH/SEARCH ALL with element-assignment path enumeration
- Fix _mark_perform compound condition marking via evaluate_tree
- Fix EVALUATE TRUE prior_false to collect all MC/DC false sets
- Add impossible path filtering (Pass A.5) with trace-to-root conflict detection
- Fix multi-line PERFORM VARYING parsing (VARYING/FROM/BY/UNTIL on separate lines)
- Remove dead code: agents.py LLM parser (replaced by rule-based _BrParser)
- 59 unit tests passing, 5 integration programs verified

AGENTS.md

@@ -0,0 +1,18 @@
+# cobol-java-v3
+
+## 工作目录
+C:\Users\marye\Desktop\2026技术大赛\cobol-java-v3
+
+## 我的模块
+cobol_testgen/
+
+## 远程仓库
+https://gittea.dev/hangshuo652/cobol-java-v3
+
+## 工作流程
+```powershell
+cd "C:\Users\marye\Desktop\2026技术大赛\cobol-java-v3"
+git add cobol_testgen/
+git commit -m "描述修改"
+git push
+```