fix(webhook): remove leading slash prepended to cluster name

The webhook server was prepending "/" to the cluster name extracted from
UserInfo.Extra (e.g. "demo-project-abc" → "/demo-project-abc") as a
workaround for the milo provider registering clusters under a
"/namespace/name" style key.

milo v0.28.1 (pulled in via the go.mod bump in v0.22.0) fixed the
provider to register clusters under just the project name — matching
exactly what the webhook already has from UserInfo.Extra. The workaround
is now counterproductive: the webhook looks up "/demo-project-abc" but
the cluster is registered as "demo-project-abc", so every Gateway
admission webhook call returns "cluster not found" and is rejected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: mattdjenkinson

internal/webhook/server.go

@@ -24,16 +24,6 @@ func (s *clusterAwareWebhookServer) Register(path string, hook http.Handler) {
 		orig := h.Handler
 		h.Handler = admission.HandlerFunc(func(ctx context.Context, req admission.Request) admission.Response {
 			c := clusterFromExtra(req.UserInfo.Extra)
-			if len(c) > 0 {
-				// The cluster names are `<namespace>/<name>` format, but Milo project
-				// discovery resources do not have namespaces and return a cluster name
-				// with a leading `/`.
-				//
-				// In the future, this should be improved to allow the multicluster-provider
-				// discovery mechanism to handle this somehow.
-
-				c = "/" + c
-			}
 			ctx = mccontext.WithCluster(ctx, multicluster.ClusterName(c))
 			return orig.Handle(ctx, req)
 		})