feat(cyberchef): Gateway-API as an alternative to the Ingress (pilot)

The Gateway-API pilot of Gitea #114: one chart, the convention, the CI that
holds it. The remaining 20 charts follow in their own PRs.

The form, additive and off by default:

    httpRoute:
      enabled: false     # counterpart to ingress.enabled
      parentRefs: []     # the Gateway - a platform object
      hostnames: []      # empty = [ingress.domain]

Only HTTPRoute with parentRefs is rendered: no Gateway, no gatewayClassName,
no Certificate, and no implementation-specific policy object. That subset is
identical on nginx-gateway-fabric, Cilium, Envoy Gateway and Istio, which is
what lets the implementation be chosen later without touching the charts
again. Class and certificate move to the platform.

Four guards, all against silent failures:

  - mutually exclusive with ingress.enabled, with a render abort naming BOTH
    value paths. A migration runs over a second hostname, not in parallel.
  - parentRefs mandatory in Gateway mode, render abort on the empty list: a
    route without a parent is created, is schema-valid, and routes nothing.
  - hostnames empty means [ingress.domain], so the hostname has one source.
  - the mode is a VALUE, not auto-detection: .Capabilities.APIVersions is
    unreliable at template time and a missing CRD fails at install time.

ingress.clusterIssuer was already only read inside the Ingress template, so
the "conditionally required" half of #114 needed no change in this chart -
checked rather than assumed, and it has to be re-checked per chart in the
sweep.

CI, both halves, because neither covers the other:

  - the install-test installs cyberchef in GATEWAY mode against the REAL
    Gateway-API CRDs (standard channel v1.6.3, pinned and Renovate-tracked,
    applied --server-side). A schema-less stub would accept a malformed route
    and prove only that something was created. The Ingress path of this one
    chart is no longer installed; it is a built-in type that never routed in
    k3d anyway, and helm lint renders this chart's defaults - Ingress mode -
    on every PR.
  - ci/run-httproute-match-test.sh, over every chart on every PR: every
    backendRefs entry must name a Service, on a port, that the SAME render
    creates, and parentRefs must not be empty. The CRDs accept both of those
    mistakes, so the schema cannot catch them, and the only report would be a
    route status no controller writes in CI.

What stays unprovable, and is written down instead of implied: that traffic
flows. No Gateway controller runs in k3d.

Minor: additive with unchanged defaults, proven by an empty helm template
diff against origin/main for the default values.

Part of #114

cyberchef/templates/NOTES.txt

@@ -1,9 +1,14 @@
 {{- $replicas := include "cyberchef.replicas" (dict "scaleDown" .Values.scaleDown "replicas" .Values.cyberchef.replicas) -}}
+{{- $httpRoute := .Values.httpRoute | default dict -}}
+{{- $hostnames := $httpRoute.hostnames | default list -}}
+{{- if not $hostnames -}}
+{{- $hostnames = list .Values.ingress.domain -}}
+{{- end -}}
 CyberChef {{ .Chart.AppVersion }} — release {{ .Release.Name }} in namespace {{ .Release.Namespace }}.
 
 {{- if .Values.ingress.enabled }}
 
-ACCESS
+ACCESS — INGRESS MODE (ingress.enabled: true, httpRoute.enabled: false)
   https://{{ .Values.ingress.domain }}
 
   The certificate is requested by cert-manager through the "{{ .Values.ingress.clusterIssuer }}"
@@ -13,31 +18,83 @@ ACCESS
 
   This chart has no secrets and no volumes — the two ingress values above are
   everything an installation needs.
+{{- else if $httpRoute.enabled }}
+
+ACCESS — GATEWAY MODE (httpRoute.enabled: true, ingress.enabled: false)
+{{- range $hostnames }}
+  https://{{ . }}
+{{- end }}
+
+  This release renders an HTTPRoute ({{ .Release.Name }}-{{ .Chart.Name }}-httproute) and NOTHING else
+  of the routing path — no Gateway, no class, no Certificate. Three things
+  therefore belong to the cluster and not to this chart, and if any of them is
+  missing the hostname above simply does not answer:
+
+    1. The Gateway-API CRDs. Without them this install would have failed, so
+       they are present — nothing to check.
+    2. The Gateway named in httpRoute.parentRefs
+{{- range $httpRoute.parentRefs }}
+         {{ .name }}{{ if .namespace }} in namespace {{ .namespace }}{{ end }}{{ if .sectionName }}, listener {{ .sectionName }}{{ end }}
+{{- end }}
+       must exist AND its listener must allow routes from this namespace
+       ({{ .Release.Namespace }}) in allowedRoutes. A rejected attachment is
+       visible only in the route's status:
+
+         kubectl -n {{ .Release.Namespace }} get httproute {{ .Release.Name }}-{{ .Chart.Name }}-httproute -o yaml
+
+       Read status.parents[].conditions — "Accepted: True" and
+       "ResolvedRefs: True" is what a working attachment looks like. An empty
+       status means no controller has looked at the route at all.
+    3. The TLS certificate for the hostname, on the Gateway's listener.
+       ingress.clusterIssuer is NOT used in this mode and is not required —
+       the chart renders no Certificate here, so there is no
+       tls-{{ .Release.Name }}-{{ .Chart.Name }}-ingress secret and nothing for cert-manager to do
+       on behalf of this release.
+
+  ingress.annotations is also inert in this mode: the Gateway API has no
+  annotation channel for controller behaviour. See the note below on who can
+  use this instance.
 {{- else }}
 
-ACCESS — NO INGRESS
-  ingress.enabled is false, so this release has no Ingress and no certificate;
-  ingress.domain and ingress.clusterIssuer are not needed. The app is only
-  reachable inside the cluster, as
-  {{ .Release.Name }}-{{ .Chart.Name }}-service:80. To open it locally:
+ACCESS — NEITHER INGRESS NOR HTTPROUTE
+  ingress.enabled and httpRoute.enabled are both false, so this release has no
+  Ingress, no HTTPRoute and no certificate; ingress.domain and
+  ingress.clusterIssuer are not needed. The app is only reachable inside the
+  cluster, as {{ .Release.Name }}-{{ .Chart.Name }}-service:80. To open it locally:
 
     kubectl -n {{ .Release.Namespace }} port-forward svc/{{ .Release.Name }}-{{ .Chart.Name }}-service 8080:80
 
-  Then browse to http://localhost:8080. Set ingress.enabled=true together with
-  ingress.domain and ingress.clusterIssuer to publish it instead.
+  Then browse to http://localhost:8080. To publish it instead, set either
+  ingress.enabled=true with ingress.domain and ingress.clusterIssuer, or
+  httpRoute.enabled=true with ingress.domain and httpRoute.parentRefs.
 {{- end }}
 {{ if eq $replicas "0" }}
 SCALED TO ZERO
   {{ if .Values.scaleDown }}scaleDown: true{{ else }}cyberchef.replicas: 0{{ end }} — the deployment runs with replicas: 0, so the endpoint
   above does not answer until you set it back and upgrade again. Service{{ if .Values.ingress.enabled }} and
-  Ingress stay in place, so the certificate is not re-issued.{{ else }} stays in
+  Ingress stay in place, so the certificate is not re-issued.{{ else if $httpRoute.enabled }} and
+  HTTPRoute stay in place, so the route keeps pointing at a Service with no
+  endpoints — the Gateway answers with an error of its own rather than with
+  nothing.{{ else }} stays in
   place.{{ end }}
 {{ end }}
 ANYONE WHO REACHES THE URL CAN USE IT
+{{- if $httpRoute.enabled }}
+  CyberChef has no login, and this chart adds none. In GATEWAY MODE there is no
+  place in this chart to put one either: the Gateway API has no annotation
+  channel, so the ingress-nginx external-auth or basic-auth annotations that
+  cover this in Ingress mode have NO counterpart here, and the chart renders no
+  implementation-specific policy object on purpose (it would bind the chart to
+  one Gateway implementation). Protection has to come from the Gateway itself —
+  a listener that is not publicly reachable, or that implementation's own auth
+  filter/policy, configured next to the Gateway and not here.
+{{- else }}
   CyberChef has no login, and this chart adds none. If it must not be open to
   everyone, put authentication in front of it via ingress.annotations — the
   chart merges them into the Ingress, e.g. ingress-nginx external auth or
-  basic auth annotations.
+  basic auth annotations. Note that this escape hatch exists in Ingress mode
+  only: httpRoute.enabled has no annotation channel at all.
+{{- end }}
 
 NOTHING TO BACK UP, NOTHING TO MIGRATE
   CyberChef is a static web app: recipes and inputs are processed in the