DP18: add getMemberName helper and dedup name-fallback sites

Add a pure `getMemberName(room, userId): string` helper in utils/room.ts
(= getMemberDisplayName ?? getMxIdLocalPart ?? userId) and replace the
inline `getMemberDisplayName(room, id) ?? getMxIdLocalPart(id) ?? id`
fallback across the codebase. No behavior change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/pages/client/ClientNonUIFeatures.tsx

@@ -27,13 +27,13 @@ import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { getDirectRoomPath, getHomeRoomPath, getInboxInvitesPath } from '../pathUtils';
 import { mDirectAtom } from '../../state/mDirectList';
 import {
-  getMemberDisplayName,
+  getMemberName,
   getNotificationType,
   getUnreadInfo,
   isNotificationEvent,
 } from '../../utils/room';
 import { NotificationType } from '../../../types/matrix/room';
-import { getMxIdLocalPart, mxcUrlToHttp } from '../../utils/matrix';
+import { mxcUrlToHttp } from '../../utils/matrix';
 import { useSelectedRoom } from '../../hooks/router/useSelectedRoom';
 import { useInboxNotificationsSelected } from '../../hooks/router/useInbox';
 import { useMediaAuthentication } from '../../hooks/useMediaAuthentication';
@@ -501,7 +501,7 @@ function MessageNotifications() {
           roomAvatar: avatarMxc
             ? (mxcUrlToHttp(mx, avatarMxc, useAuthentication, 96, 96, 'crop') ?? undefined)
             : undefined,
-          username: getMemberDisplayName(room, sender) ?? getMxIdLocalPart(sender) ?? sender,
+          username: getMemberName(room, sender),
           roomId: room.roomId,
           eventId,
           body: (mEvent.getContent().body as string | undefined) ?? '',

src/app/pages/client/inbox/Invites.tsx

@@ -37,7 +37,7 @@ import {
   bannedInRooms,
   getCommonRooms,
   getDirectRoomAvatarUrl,
-  getMemberDisplayName,
+  getMemberName,
   getRoomAvatarUrl,
   getStateEvent,
   isDirectInvite,
@@ -48,7 +48,6 @@ import { RoomAvatar } from '../../../components/room-avatar';
 import {
   addRoomIdToMDirect,
   declineInvite,
-  getMxIdLocalPart,
   guessDmRoomUserId,
   rateLimitedActions,
 } from '../../../utils/matrix';
@@ -107,9 +106,7 @@ const makeInviteData = (mx: MatrixClient, room: Room, useAuthentication: boolean
   const content = memberEvent?.getContent();
   const senderId = memberEvent?.getSender();
 
-  const senderName = senderId
-    ? (getMemberDisplayName(room, senderId) ?? getMxIdLocalPart(senderId) ?? senderId)
-    : undefined;
+  const senderName = senderId ? getMemberName(room, senderId) : undefined;
   const inviteTs = memberEvent?.getTs();
   const reason =
     content && 'reason' in content && typeof content.reason === 'string'

src/app/pages/client/inbox/Notifications.tsx

@@ -28,7 +28,7 @@ import { Opts as LinkifyOpts } from 'linkifyjs';
 import { useAtomValue } from 'jotai';
 import { Page, PageContent, PageContentCenter, PageHeader } from '../../../components/page';
 import { useMatrixClient } from '../../../hooks/useMatrixClient';
-import { getMxIdLocalPart, mxcUrlToHttp } from '../../../utils/matrix';
+import { mxcUrlToHttp } from '../../../utils/matrix';
 import { InboxNotificationsPathSearchParams } from '../../paths';
 import { AsyncStatus, useAsyncCallback } from '../../../hooks/useAsyncCallback';
 import { SequenceCard } from '../../../components/sequence-card';
@@ -36,7 +36,7 @@ import { RoomAvatar, RoomIcon } from '../../../components/room-avatar';
 import {
   getEditedEvent,
   getMemberAvatarMxc,
-  getMemberDisplayName,
+  getMemberName,
   getRoomAvatarUrl,
 } from '../../../utils/room';
 import { ScrollTopContainer } from '../../../components/scroll-top-container';
@@ -448,10 +448,7 @@ function RoomNotificationsGroupComp({
         {notifications.map((notification) => {
           const { event } = notification;
 
-          const displayName =
-            getMemberDisplayName(room, event.sender) ??
-            getMxIdLocalPart(event.sender) ??
-            event.sender;
+          const displayName = getMemberName(room, event.sender);
           const senderAvatarMxc = getMemberAvatarMxc(room, event.sender);
           const getContent = (() => event.content) as GetContentCallback;