Say where the one-gate rule applies, and record why allows stays open

AGENTS.md

@@ -186,7 +186,9 @@ Revisit only if the stated reason stops holding.
   node names exactly one of `public`, `session`, `permission` — discovery refuses none, two, and a
   flag spelled anything but `true`, so a forgotten gate fails the boot rather than publishing a page.
   `src/auth/gate.ts` is the one home of the rule the plugin router, the host's own route table and
-  the menu all read. `session` exists because a plugin whose data is
+  the menu all read. Exactly-one-gate is a discovery-time rule on manifests, not a runtime invariant:
+  `allows({}, user)` stays open **by design**, because the central override's `groups` builds header
+  nodes that carry no gate. Making `allows` fail closed would hide every operator-grouped section. `session` exists because a plugin whose data is
   the visitor's own — their upstream account, their own tokens — has no distinction a permission could
   name; the alternative, granting every newly registered user a permission, couples the identity
   lifecycle to a Keto write that nothing retries when it fails. A page scoped to "mine" joins on

README.md

@@ -920,9 +920,10 @@ The menu is **driven entirely by config** and assembled from two sources:
    export default defineMenu({ branding: { name: "Acme Ops" }, override: { hide: ["teams"] } });
    ```
 
-Every nav item names one gate — a `permission`, **`public: true`** (everyone) or **`session: true`**
-(anyone signed in); the rendered tree is **filtered per user** from the session JWT (no per-request
-authz call), so the menu only shows what that person can reach.
+Every nav node a **plugin** declares names one gate — a `permission`, **`public: true`** (everyone)
+or **`session: true`** (anyone signed in); a header this override groups takes none, and shows
+whenever a child does. The rendered tree is **filtered per user** from the session JWT (no
+per-request authz call), so the menu only shows what that person can reach.
 Branding (name, logo, default theme) renders in the app shell.
 
 **One menu, one shell, everywhere.** A single menu (`src/ui/chrome.ts` `buildPluginChrome`) renders

examples/plugins/admin/admin-shared.ts

@@ -35,10 +35,9 @@ export function actionForMethod(method: string): AdminAction {
   return verb === "GET" || verb === "HEAD" ? "read" : "write";
 }
 
-// The plugin's nav fragment: an ungated "Admin" header + its three screens, each gated on its own
-// read permission. The header carries no `permission` because a user may hold one screen's and not
-// another's; composeNav drops a header left with no visible children, so a user holding none of the
-// three never sees the section. The host current-marks the active item — no `current`/`open` here.
+// The plugin's nav fragment: the "Admin" header + its four screens, each gated on its own read
+// permission. composeNav drops a header left with no visible children, so a user holding none of
+// them never sees the section. The host current-marks the active item — no `current`/`open` here.
 export const ADMIN_NAV: NavNode = {
   children: [
     { href: ADMIN_USERS_BASE, icon: "i-users", id: "users", label: "admin.nav.users", permission: permissionName("users", "read") },