Follow-up to #67675 addressing post-merge review feedback from @Miretpl. The
original PR has not been released yet, so these refinements land before the
upcoming chart release as requested.

Changes:

• Move the HTTPRoute config from top-level httpRoute.apiServer.* to
  apiServer.httpRoute.* — it is an API-server setting, not a global one
  (values.yaml, values.schema.json, template, docs, tests).
• Fail template rendering with a clear message when apiServer.httpRoute.enabled
  is true but the Gateway API HTTPRoute CRD is not installed (via
  .Capabilities.APIVersions.Has).
• Fail when both ingress.apiServer.enabled and apiServer.httpRoute.enabled
  are set — HTTPRoute is an alternative to the API server Ingress.
• Strengthen tests: assert full spec.parentRefs / spec.rules structures, add
  asserts to the validation test, inline a single-use variable, and split the
  parametrized creation test into separate cases (no inner if).
• Add an api_versions parameter to the render_chart helper so
  Capabilities-gated templates render offline.

Validation:

• 48 apiserver helm unit tests pass (incl. new CRD-missing and ingress-conflict cases)
• helm template renders for enabled/disabled and fails as expected for both guards
• chart-quality (values↔schema) test passes; ruff clean

related: #67675

Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Opus 4.8)

Generated-by: Claude Code (Opus 4.8) following the guidelines