Add a Conftest evaluation example

[kmadan]

Goal

Demonstrate evaluating GOPAL policies via Conftest — the most common OPA front-end for non-Kubernetes use cases.

Why this matters

Many platform teams already use Conftest in CI for Terraform, Kubernetes manifests, or Dockerfiles. Showing Conftest + GOPAL widens the addressable user base directly into the OPA ecosystem without asking anyone to learn new tooling.

Files likely involved

• `examples/conftest/README.md` (new) — Conftest mental model vs raw `opa eval`
• `examples/conftest/policy/` (new) — symlink, vendor, or import-only Rego pointing at GOPAL
• `examples/conftest/input.json` (new) — sample AI-system payload
• `examples/conftest/run.sh` (new) — wraps `conftest test input.json -p policy/`

Acceptance criteria

• `./run.sh` runs Conftest against a GOPAL policy and produces a structured pass/fail
• README documents the Conftest install step and any caveats (e.g., bundle path, namespace)
• At least one failing-case input demonstrates a non-zero exit code
• `examples/README.md` links to the new example

Get help

Comment here. Existing Conftest experience helpful but not required.