fix(mobile): member list no longer opens on top of every room on phones (#175)

Room.tsx showed the MembersDrawer on phone widths whenever the persisted
desktop preference isPeopleDrawer was true — which is the default — so a
new mobile session opened every room behind a full-screen member list.
Mobile now uses a transient mobileMembersPanelAtom (header ⋮ → Members
toggles it, the drawer's X closes it, leaving the room resets it); the
desktop drawer keeps using the setting. Verified with Playwright at 400px.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/room/Room.tsx

@@ -2,13 +2,14 @@ import React, { useCallback, useEffect, useRef } from 'react';
 import { Box, Line } from 'folds';
 import { useParams } from 'react-router-dom';
 import { isKeyHotkey } from 'is-hotkey';
-import { useAtomValue, useSetAtom } from 'jotai';
+import { useAtom, useAtomValue, useSetAtom } from 'jotai';
 import { RoomView } from './RoomView';
 import { MembersDrawer } from './MembersDrawer';
 import { MediaGallery } from './MediaGallery';
 import { mediaGalleryAtom } from '../../state/mediaGallery';
 import { WidgetsPanel } from './widgets/WidgetsPanel';
 import { widgetsPanelAtom } from '../../state/widgetsPanel';
+import { mobileMembersPanelAtom } from '../../state/mobileMembersPanel';
 import { ScreenSize, useScreenSizeContext } from '../../hooks/useScreenSize';
 import { useSetting } from '../../state/hooks/settings';
 import { settingsAtom } from '../../state/settings';
@@ -46,6 +47,7 @@ export function Room() {
   const galleryOpen = useAtomValue(mediaGalleryAtom);
   const setGalleryOpen = useSetAtom(mediaGalleryAtom);
   const widgetsOpen = useAtomValue(widgetsPanelAtom);
+  const [mobileMembersOpen, setMobileMembersOpen] = useAtom(mobileMembersPanelAtom);
   const setWidgetsOpen = useSetAtom(widgetsPanelAtom);
   const threadsListOpen = useAtomValue(threadsListAtom);
   const setThreadsListOpen = useSetAtom(threadsListAtom);
@@ -146,10 +148,16 @@ export function Room() {
     threadsListOpen &&
     !activeThreadId &&
     (isDesktop || (!galleryOpen && !widgetsOpen));
+  // Desktop: the persisted drawer preference. Mobile: a transient panel the
+  // user opened from the header menu (never the desktop default).
   const showMembers =
     !callView &&
-    isDrawer &&
-    (isDesktop || (!activeThreadId && !galleryOpen && !widgetsOpen && !threadsListOpen));
+    (isDesktop
+      ? isDrawer
+      : mobileMembersOpen && !activeThreadId && !galleryOpen && !widgetsOpen && !threadsListOpen);
+
+  // Leaving a room on a phone closes its member panel.
+  useEffect(() => () => setMobileMembersOpen(false), [room.roomId, setMobileMembersOpen]);
 
   return (
     <PowerLevelsContextProvider value={powerLevels}>