[WIP] Complete test cases for src/cuddCof.c to target 90% coverage

[Copilot]

• Analyze source file src/cuddCof.c and understand functions to test
• Run initial coverage build and identify coverage gaps (10.4% initially)
• Write comprehensive tests for Cudd_Cofactor function including error paths
• Write comprehensive tests for Cudd_CheckCube function
• Write comprehensive tests for Cudd_VarsAreSymmetric function
• Write comprehensive tests for cuddGetBranches function
• Write comprehensive tests for cuddCofactorRecur function paths
• Write comprehensive tests for ddVarsAreSymmetricBefore function
• Write comprehensive tests for ddVarsAreSymmetricBetween function
• Verify 90%+ coverage is achieved (94.6% - 159/168 lines covered)
• Fix code review issues (proper memory management for intermediate BDD nodes)
• Pass CodeQL security check (0 alerts)

Original prompt

Complete test cases for src/cuddCof.c and target 90% coverage for the source file.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.