feat(workspace): gate Echo Studio scaffold behind off-by-default Labs toggle

Echo Studio (integrated from #457 in cycle 2b) was always-visible in the
chat sidebar and mobile hamburger nav. It's a scaffold/prototype, so surface
it only when opted in.

- add experimentalEchoStudio: false to StudioSettings + defaults
- new Settings > Labs (experimental) section with a Switch
- chat-sidebar + mobile-hamburger filter the Echo Studio nav item by the flag

src/components/mobile-hamburger-menu.tsx

@@ -26,6 +26,7 @@ import {
   selectChatProfileDisplayName,
   useChatSettingsStore,
 } from '@/hooks/use-chat-settings'
+import { useSettingsStore } from '@/hooks/use-settings'
 
 export const MOBILE_HAMBURGER_NAV_ITEMS = [
   {
@@ -166,6 +167,12 @@ export function MobileHamburgerMenu() {
   const navigate = useNavigate()
   const pathname = useRouterState({ select: (s) => s.location.pathname })
   const profileDisplayName = useChatSettingsStore(selectChatProfileDisplayName)
+  const echoStudioEnabled = useSettingsStore(
+    (state) => state.settings.experimentalEchoStudio,
+  )
+  const visibleNavItems = MOBILE_HAMBURGER_NAV_ITEMS.filter(
+    (item) => item.id !== 'echo-studio' || echoStudioEnabled,
+  )
   const isChatRoute =
     pathname.startsWith('/chat') || pathname === '/new' || pathname === '/'
 
@@ -253,7 +260,7 @@ export function MobileHamburgerMenu() {
 
         {/* Nav items */}
         <nav className="flex flex-col gap-1 px-3 pt-4 flex-1">
-          {MOBILE_HAMBURGER_NAV_ITEMS.map((item) => {
+          {visibleNavItems.map((item) => {
             const isActive = item.match(pathname)
             return (
               <button

src/hooks/use-settings.ts

@@ -28,6 +28,8 @@ export type StudioSettings = {
   interfaceDensity: InterfaceDensity
   /** Mobile chat nav mode: 'dock' = iMessage (no nav in chat), 'integrated' = chat input in nav pill, 'scroll-hide' = nav shows on scroll up */
   mobileChatNavMode: 'dock' | 'integrated' | 'scroll-hide'
+  /** Hidden experimental: show Echo Studio (dashboard builder scaffold) in nav. Off by default. */
+  experimentalEchoStudio: boolean
 }
 
 type SettingsState = {
@@ -54,6 +56,7 @@ export const defaultStudioSettings: StudioSettings = {
   interfaceFont: 'system',
   interfaceDensity: 'comfortable',
   mobileChatNavMode: 'dock',
+  experimentalEchoStudio: false,
 }
 
 export const useSettingsStore = create<SettingsState>()(

src/routes/settings/index.tsx

@@ -427,6 +427,25 @@ function SettingsRoute() {
                   </div>
                 </div>
               </SettingsSection>
+
+              <SettingsSection
+                title="Labs (experimental)"
+                description="Early/unfinished features. May change or be removed. Off by default."
+                icon={Settings02Icon}
+              >
+                <SettingsRow
+                  label="Echo Studio"
+                  description="Show the Echo Studio dashboard builder (scaffold) in the nav. Experimental."
+                >
+                  <Switch
+                    checked={settings.experimentalEchoStudio}
+                    onCheckedChange={(checked) =>
+                      updateSettings({ experimentalEchoStudio: checked })
+                    }
+                    aria-label="Enable Echo Studio (experimental)"
+                  />
+                </SettingsRow>
+              </SettingsSection>
             </>
           )}
 

src/screens/chat/components/chat-sidebar.tsx

@@ -587,6 +587,9 @@ function ChatSidebarComponent({
   const isConductorActive = pathname === '/conductor'
   const isOperationsActive = pathname === '/operations'
   const isSwarmActive = pathname === '/swarm' || pathname === '/swarm2'
+  const echoStudioEnabled = useSettingsStore(
+    (state) => state.settings.experimentalEchoStudio,
+  )
   const mainRoutes = ['/chat', '/new', '/files', '/terminal']
   const knowledgeRoutes = ['/memory', '/skills']
   const systemRoutes = ['/settings', '/logs']
@@ -845,13 +848,17 @@ function ChatSidebarComponent({
       label: 'Swarm',
       active: isSwarmActive,
     },
-    {
-      kind: 'link',
-      to: '/echo-studio',
-      icon: DashboardSquare01Icon,
-      label: 'Echo Studio',
-      active: pathname.startsWith('/echo-studio'),
-    },
+    ...(echoStudioEnabled
+      ? [
+          {
+            kind: 'link' as const,
+            to: '/echo-studio',
+            icon: DashboardSquare01Icon,
+            label: 'Echo Studio',
+            active: pathname.startsWith('/echo-studio'),
+          },
+        ]
+      : []),
 
   ]