Fix presence showing offline on non-chat pages, and a room-join bug it exposed

The WebSocket connection lived entirely inside ChatShellPage, so
navigating to /admin (which never opens its own connection) unmounted
it -- the server correctly marked the user offline since the
connection genuinely closed, even though they were still logged in
and using the app. New ChatSocketContext.tsx hoists the connection to
App.tsx, shared across every authenticated route via a single
provider (keyed by user id, so a logout/login as a different account
gets a clean reconnect rather than an old connection lingering under
a new identity) instead of living inside whichever page happens to be
mounted.

Verifying that fix surfaced a second, independent bug: #31's
visibility handling had gated the *explicit* joinRoom/leaveRoom calls
(fired when a room actually mounts/unmounts in the UI) on the same
isVisibleRef check meant for automatic background/foreground
transitions. That's wrong -- a room can only be opened by a real user
interaction, which can't happen on a genuinely backgrounded tab, so
gating it too meant a stale or momentarily-wrong visibility reading
at mount time could silently skip the join with nothing to ever retry
it. joinRoom/leaveRoom now always send immediately; only the
automatic hide/show transitions and the reconnect replay stay gated
on visibility, which is what #31 actually needed.

Verified both end-to-end in the browser: navigating to /admin via
real in-app navigation (not a reload) keeps the presence dot online,
confirmed via direct Redis inspection and the /api/users/online
endpoint; opening a room and sending a message works immediately
afterward.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -1,5 +1,6 @@
 import { Navigate, Route, Routes } from 'react-router-dom'
-import { AuthProvider } from './context/AuthContext'
+import { AuthProvider, useAuth } from './context/AuthContext'
+import { ChatSocketProvider } from './context/ChatSocketContext'
 import { AdminRoute } from './components/AdminRoute'
 import { ProtectedRoute } from './components/ProtectedRoute'
 import { UpdateBanner } from './components/UpdateBanner'
@@ -10,10 +11,8 @@ import { ResetPasswordPage } from './pages/ResetPasswordPage'
 import { ChatShellPage } from './pages/ChatShellPage'
 import { AdminPage } from './pages/AdminPage'
 
-function App() {
-  return (
-    <AuthProvider>
-      <UpdateBanner />
+function AppRoutes() {
+  const routes = (
     <Routes>
       <Route path="/login" element={<LoginPage />} />
       <Route path="/signup" element={<SignupPage />} />
@@ -45,6 +44,25 @@ function App() {
       />
       <Route path="*" element={<Navigate to="/rooms" replace />} />
     </Routes>
+  )
+
+  // Only while actually logged in -- and keyed by user id so switching
+  // which account is logged in (same tab) tears down and re-establishes a
+  // fresh connection rather than an old one lingering under a new
+  // identity. Wraps every authenticated route (not just ChatShellPage),
+  // since the connection backs the presence indicator and cross-page
+  // signals (e.g. "added to a room") that matter regardless of which page
+  // is currently open.
+  const { user } = useAuth()
+  if (!user) return routes
+  return <ChatSocketProvider key={user.id}>{routes}</ChatSocketProvider>
+}
+
+function App() {
+  return (
+    <AuthProvider>
+      <UpdateBanner />
+      <AppRoutes />
     </AuthProvider>
   )
 }

frontend/src/context/ChatSocketContext.tsx

@@ -0,0 +1,25 @@
+import { createContext, useCallback, useContext, type ReactNode } from 'react'
+import { useNavigate } from 'react-router-dom'
+import { useChatSocket, type ChatSocketHandle } from '../ws/useChatSocket'
+
+const ChatSocketContext = createContext<ChatSocketHandle | undefined>(undefined)
+
+// One connection for the whole authenticated session, not just whichever
+// page happens to be mounted -- previously this lived inside
+// ChatShellPage, so navigating to a page that isn't ChatShellPage (e.g.
+// /admin) unmounted it, closing the connection. The server correctly
+// read that as "this user is no longer connected," which made a logged-in
+// admin looking at the admin page show up as offline everywhere else
+// (the presence dot reads this same connection).
+export function ChatSocketProvider({ children }: { children: ReactNode }) {
+  const navigate = useNavigate()
+  const onUnauthenticated = useCallback(() => navigate('/login'), [navigate])
+  const socket = useChatSocket({ onUnauthenticated })
+  return <ChatSocketContext.Provider value={socket}>{children}</ChatSocketContext.Provider>
+}
+
+export function useChatSocketContext(): ChatSocketHandle {
+  const ctx = useContext(ChatSocketContext)
+  if (!ctx) throw new Error('useChatSocketContext must be used within a ChatSocketProvider')
+  return ctx
+}

frontend/src/pages/ChatShellPage.tsx

@@ -10,9 +10,9 @@ import { RoomInfoPanel } from '../components/RoomInfoPanel'
 import { Sidebar } from '../components/Sidebar'
 import { TopBar } from '../components/TopBar'
 import { useAuth } from '../context/AuthContext'
+import { useChatSocketContext } from '../context/ChatSocketContext'
 import { MOBILE_BREAKPOINT, useWindowWidth } from '../hooks/useWindowWidth'
 import type { MyRoomItem, RoomMember } from '../types'
-import { useChatSocket } from '../ws/useChatSocket'
 import './ChatShellPage.css'
 
 type ModalKind = 'new' | 'browse' | null
@@ -57,8 +57,7 @@ export function ChatShellPage() {
     refreshRooms().catch(() => {})
   }, [refreshRooms])
 
-  const onSocketUnauthenticated = useCallback(() => navigate('/login'), [navigate])
-  const socket = useChatSocket({ onUnauthenticated: onSocketUnauthenticated })
+  const socket = useChatSocketContext()
 
   useEffect(
     () =>

frontend/src/ws/useChatSocket.ts

@@ -135,7 +135,20 @@ export function useChatSocket({ onUnauthenticated }: UseChatSocketOptions) {
   const joinRoom = useCallback(
     (roomId: string) => {
       desiredRoomsRef.current.add(roomId)
-      if (isVisibleRef.current) sendRoomFrame('join', roomId)
+      // Unconditional, not gated on isVisibleRef: this fires from a
+      // component actually mounting (opening a room in the UI), which by
+      // definition only happens while the user is interacting with the
+      // page -- a genuinely backgrounded tab can't run the click handler
+      // that leads here in the first place. Gating this too (rather than
+      // only the automatic hide/show transitions below) meant a stale or
+      // momentarily-wrong visibilityState at mount time could silently
+      // skip the join entirely, with nothing to ever retry it. Also
+      // self-corrects isVisibleRef -- opening a room this way is itself
+      // stronger evidence of visibility than whatever the ref currently
+      // holds, so a wrong/stale `false` doesn't also skip replaying this
+      // join on a later reconnect (which does still check the ref).
+      isVisibleRef.current = true
+      sendRoomFrame('join', roomId)
     },
     [sendRoomFrame],
   )
@@ -143,7 +156,7 @@ export function useChatSocket({ onUnauthenticated }: UseChatSocketOptions) {
   const leaveRoom = useCallback(
     (roomId: string) => {
       desiredRoomsRef.current.delete(roomId)
-      if (isVisibleRef.current) sendRoomFrame('leave', roomId)
+      sendRoomFrame('leave', roomId)
     },
     [sendRoomFrame],
   )