rbac: add fission-executor-sa-provisioner for SA/Role/RoleBinding creation in user NS

Fixes EnsureNamespaceSA getting 403 Forbidden when provisioning fission-fetcher
SA in dynamically registered namespaces. Adds ClusterRole + ClusterRoleBinding
with create/update/patch for serviceaccounts, roles, rolebindings.

Also adds doc/progress.md and doc/thinking/2026-04-26-rbac-fix.md.

deploy/multitenant/rbac.yaml

@@ -40,3 +40,38 @@ subjects:
   - kind: ServiceAccount
     name: fission-executor
     namespace: fission
+---
+# ClusterRole: allows fission-executor to create/update fission-fetcher SA,
+# Role and RoleBinding in any user namespace managed by NSWatcher.
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: fission-executor-sa-provisioner
+  labels:
+    app.kubernetes.io/name: fission
+    app.kubernetes.io/component: executor
+    app.kubernetes.io/part-of: fission-multitenant
+rules:
+  - apiGroups: [""]
+    resources: ["serviceaccounts"]
+    verbs: ["get", "list", "watch", "create", "update", "patch"]
+  - apiGroups: ["rbac.authorization.k8s.io"]
+    resources: ["roles", "rolebindings"]
+    verbs: ["get", "list", "watch", "create", "update", "patch"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: fission-executor-sa-provisioner
+  labels:
+    app.kubernetes.io/name: fission
+    app.kubernetes.io/component: executor
+    app.kubernetes.io/part-of: fission-multitenant
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: fission-executor-sa-provisioner
+subjects:
+  - kind: ServiceAccount
+    name: fission-executor
+    namespace: fission