Add tests for Kubernetes Helm value rendering

[MuttleyD]

Context

The MIDAS Helm chart now renders a numeric non-root pod security context by default. This was added after local kind validation showed that Kubernetes could not start the MIDAS distroless image when runAsNonRoot: true was set without numeric runAsUser and runAsGroup values.

The chart is currently validated manually with:

helm lint charts/midas
helm template midas charts/midas --namespace midas -f examples/kubernetes/kind-values.yaml

A small test would help prevent future changes from accidentally removing or breaking the rendered security context.

Scope

Add or extend a test that renders the Helm chart and verifies the Deployment includes the expected pod security context.

The test should confirm that the rendered Deployment includes:

securityContext:
  runAsNonRoot: true
  runAsUser: 65532
  runAsGroup: 65532
  seccompProfile:
    type: RuntimeDefault

It should also confirm the container hardening remains present:

allowPrivilegeEscalation: false
readOnlyRootFilesystem: true
capabilities:
  drop:
    - ALL

Recommended area to inspect first:

cmd/midas/helm_pool_values_test.go
charts/midas/values.yaml
charts/midas/templates/deployment.yaml

Acceptance Criteria

• A test verifies the chart renders numeric non-root pod security context values.
• A test verifies the container security context still disables privilege escalation, uses a read-only root filesystem, and drops capabilities.
• The test uses the existing test style in the repository.
• No runtime behaviour is changed.
• No chart values are changed unless the test reveals a clear existing mismatch.
• go test ./cmd/midas passes.
• helm lint charts/midas passes if Helm is available.
• git diff --check passes.

Out of Scope

• Changing the Helm chart security model.
• Adding new Helm features.
• Adding CI infrastructure.
• Adding Kubernetes runtime tests.
• Changing Docker image behaviour.