feat(chart): parameterize image refs with registrySuffix (drop hardcoded "/")

[elronbandel]

Why

The shared Helm chart's three image refs hardcode the category/name separator as / — registry/core/otel, registry/models/<x>, registry/evals/<x>. That blocks rendering against a flattened internal registry, notably an OpenShift imagestream: a namespace can't hold nested paths, so images must collapse to core-otel. This is the Helm-side gap that #23 closed for the Dockerfiles.

What

Mirror PR #23's REGISTRY_SUFFIX parameterization in the chart. Add .Values.registrySuffix (default "/"), placed between category and name exactly as the Dockerfiles do (${REGISTRY}/<cat>${REGISTRY_SUFFIX}<name>):

{{ .Values.registry }}/core{{ .Values.registrySuffix }}otel:latest
{{ .Values.registry }}/models{{ .Values.registrySuffix }}{{ .Values.gatewayImage }}:{{ .Values.gatewayTag }}
{{ .Values.registry }}/evals{{ .Values.registrySuffix }}{{ .Values.benchmark }}--{{ .Values.agent }}:{{ .Values.runnerTag }}

Byte-identical at the default: "/" resolves to today's refs exactly. The only new capability is --set registrySuffix=-, which flattens every image to registry/<cat>-<name>. Like the other platform knobs, it's meant to be set once in an overlay (deploy/values-openshift.yaml) via --overlay, not per run — matching the project's axis(--set)/platform(--overlay) split. No CLI change: the CLI already threads --set registry= and layers overlays; the suffix rides the overlay.

Verification

• aime renders byte-identical to main at defaults (diff empty).
• --set registry=…/myns --set registrySuffix=- → …/myns/core-otel, …/myns/models-…, …/myns/evals-aime--claude-code (flattened imagestream form).
• All 102 benchmarks pass cargo test --test helm.

Companion to #23 for the build --builder oc / OpenShift-internal-registry path.