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/values.schema.json

@@ -57,13 +57,42 @@
           "type": ["string", "null"]
         },
         "annotations": {
-          "description": "Extra Ingress annotations, merged with the cert-manager annotation the chart always sets. Free-form keys by nature.",
+          "description": "Extra Ingress annotations, merged with the cert-manager annotation the chart always sets. Free-form keys by nature. No counterpart in Gateway mode: the Gateway API has no annotation channel, so these are gone when httpRoute.enabled is used instead.",
           "type": "object"
         }
       }
+    },
+    "httpRoute": {
+      "description": "Gateway-API alternative to the Ingress (Gitea #114). Mutually exclusive with ingress.enabled - the render aborts when both are true. The chart renders only an HTTPRoute with parentRefs; class and certificate sit on the Gateway and belong to the platform. The Gateway-API CRDs must be present in the cluster, because the chart cannot detect them.",
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "enabled": {
+          "type": "boolean"
+        },
+        "parentRefs": {
+          "description": "The Gateway(s) the route attaches to. Required while httpRoute.enabled is true, enforced by required()-equivalent in the template (an empty list aborts the render) - a JSON Schema \"required\" cannot do it, because the key ships as an empty list and is therefore present. Entries are the Gateway API's ParentReference and are passed through unchanged.",
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/parentRef"
+          }
+        },
+        "hostnames": {
+          "description": "Empty means [ingress.domain], so the hostname has a single source of truth.",
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        }
+      }
     }
   },
   "definitions": {
+    "parentRef": {
+      "description": "A Gateway API ParentReference, passed verbatim into HTTPRoute.spec.parentRefs. Deliberately left OPEN (no additionalProperties: false), for the same reason probes and security contexts are: Kubernetes owns this schema, the Gateway API adds fields to it across releases, and a closed list here would reject a field only upstream knows about. What the chart can assert is that \"name\" is there - it is required by the API and a reference without it attaches to nothing, which is the silent failure this chart aborts the render over.",
+      "type": "object",
+      "required": ["name"]
+    },
     "resources": {
       "description": "May be null / empty: the chart then falls back to its default requests and computed limits (issue #99) instead of rendering a container without resource accounting.",
       "type": ["object", "null"],