fix: three code review issues — leaveGroup duplicate, as any casts, federation ownership fallback

- Remove redundant `leaveGroup` API method from client.ts (duplicated `leave`); update MessageList.tsx WelcomeHeader to call `api.dm.leave` directly
- Add optional `type` field to shared `Message` interface so `MessageWithUser` carries it; remove `(msg as any).type` casts in `isSameGroup` and the render branch in MessageList.tsx
- Fix `processOwnershipTransferEvent` in federation.ts: replace `channel.ownerId` fallbacks (pre-update, old owner) with `event.ownership.newOwner.homeUserId` in the db update, dm_owner_updated broadcast, and both system message content payloads

packages/server/src/routes/federation.ts

@@ -1965,7 +1965,7 @@ function processOwnershipTransferEvent(
 
   db.update(schema.dmChannels)
     .set({
-      ownerId: newOwnerLocal?.id ?? channel.ownerId,
+      ownerId: newOwnerLocal?.id ?? null,
       ownerHomeUserId: event.ownership.newOwner.homeUserId,
       ownerHomeInstance: event.ownership.newOwner.homeInstance,
     })
@@ -1975,7 +1975,7 @@ function processOwnershipTransferEvent(
   connectionManager.sendToDmMembers(channel.id, {
     type: 'dm_owner_updated',
     dmChannelId: channel.id,
-    newOwnerId: newOwnerLocal?.id ?? channel.ownerId!,
+    newOwnerId: newOwnerLocal?.id ?? event.ownership.newOwner.homeUserId,
   });
 
   const prevOwnerLocal = event.ownership.previousOwner
@@ -1991,7 +1991,7 @@ function processOwnershipTransferEvent(
     userId: prevOwnerId,
     content: JSON.stringify({
       event: 'owner_changed',
-      newOwnerId: newOwnerLocal?.id ?? channel.ownerId,
+      newOwnerId: newOwnerLocal?.id ?? event.ownership.newOwner.homeUserId,
       newOwnerDisplayName: newOwnerLocal?.displayName ?? newOwnerBaseName,
     }),
     type: 'system',
@@ -2006,7 +2006,7 @@ function processOwnershipTransferEvent(
       userId: prevOwnerId,
       content: JSON.stringify({
         event: 'owner_changed',
-        newOwnerId: newOwnerLocal?.id ?? channel.ownerId,
+        newOwnerId: newOwnerLocal?.id ?? event.ownership.newOwner.homeUserId,
         newOwnerDisplayName: newOwnerLocal?.displayName ?? newOwnerBaseName,
       }),
       type: 'system',

packages/shared/src/types.ts

@@ -193,6 +193,7 @@ export interface Message {
   userId: string;
   replyToId: string | null;
   content: string | null;
+  type?: 'user' | 'system';
   editedAt: number | null;
   createdAt: number;
 }

packages/web/src/api/client.ts

@@ -145,7 +145,6 @@ export class BackspaceApiClient {
     deleteMessage: (id: string) => Promise<{ success: boolean }>;
     addMember: (dmChannelId: string, data: { userId: string }) => Promise<DmChannel>;
     leave: (dmChannelId: string) => Promise<{ success: boolean }>;
-    leaveGroup: (dmChannelId: string) => Promise<{ success: boolean }>;
   };
 
   readonly social: {
@@ -506,8 +505,6 @@ export class BackspaceApiClient {
         request<DmChannel>('POST', `/dm/${dmChannelId}/members`, data),
       leave: (dmChannelId: string) =>
         request<{ success: boolean }>('DELETE', `/dm/${dmChannelId}/members`),
-      leaveGroup: (dmChannelId: string) =>
-        request<{ success: boolean }>('DELETE', `/dm/${dmChannelId}/members`),
     };
 
     this.social = {

packages/web/src/components/chat/MessageList.tsx

@@ -21,7 +21,7 @@ interface MessageListProps {
 }
 
 function isSameGroup(prev: MessageWithUser, curr: MessageWithUser): boolean {
-  if ((prev as any).type === 'system' || (curr as any).type === 'system') return false;
+  if (prev.type === 'system' || curr.type === 'system') return false;
   if (prev.userId !== curr.userId) return false;
   const timeDiff = curr.createdAt - prev.createdAt;
   return timeDiff < 5 * 60 * 1000; // 5 minutes
@@ -338,7 +338,7 @@ export function MessageList({ channelId, jumpToMessageId, onJumpComplete }: Mess
                     <div className="flex-1 h-[1px] bg-border-hard" />
                   </div>
                 )}
-                {(msg as any).type === 'system' ? (
+                {msg.type === 'system' ? (
                   <SystemMessage message={msg} />
                 ) : (
                   <Message
@@ -438,7 +438,7 @@ function WelcomeHeader({ channelId }: { channelId: string }) {
 
       const handleLeaveGroup = async () => {
         try {
-          await api.dm.leaveGroup(channelId);
+          await api.dm.leave(channelId);
           navigate('/channels/@me');
         } catch (err) {
           console.error('Failed to leave group:', err);