CI/CD: Automate C++ benchmark and verification tests run in GitHub Actions workflow

[harsharajkumar-273]

Problem Description

The current .github/workflows/ci.yml pipeline successfully builds the C++ binaries using CMake, but it does not execute the compiled output or benchmarks. Testing for regression or runtime crashes (e.g. segfaults) is currently manual.

Proposed Enhancement

Update ci.yml to run the compiled binaries inside the test runner:

1. After cmake --build build, run the C++ benchmark executable: ./build/bench_repost
2. Add a simple CTest validation suite to verify that the generated outputs match expected outputs under test scenarios.