feat(web): filter remote DMs from populateFromReady, remove dedup and dead code

DMs now come exclusively from the home instance's ready payload.
Remote origins' DM channels are ignored. The deduplication logic
that preferred home copies over remote copies is no longer needed.
Removed dead loadDmChannels() (zero call sites).

packages/web/src/stores/spaceStore.ts

@@ -58,7 +58,6 @@ interface SpaceState {
   leaveDm: (id: string) => Promise<void>;
   loadSpaces: () => Promise<void>;
   loadSpaceDetail: (spaceId: string) => Promise<void>;
-  loadDmChannels: () => Promise<void>;
   createSpace: (data: CreateSpaceRequest) => Promise<Space>;
   updateSpace: (spaceId: string, data: UpdateSpaceRequest) => Promise<void>;
   deleteSpace: (spaceId: string) => Promise<void>;
@@ -282,15 +281,6 @@ export const useSpaceStore = create<SpaceState>((set, get) => ({
     }
   },
 
-  loadDmChannels: async () => {
-    try {
-      const dmChannels = await api.dm.list();
-      set({ dmChannels });
-    } catch {
-      // Handle error silently
-    }
-  },
-
   createSpace: async (data: CreateSpaceRequest) => {
     const space = await api.spaces.create(data);
     const tagged: TaggedSpace = { ...space, _instanceOrigin: '' };
@@ -653,21 +643,26 @@ export const useSpaceStore = create<SpaceState>((set, get) => ({
       }
     }
 
-    // DM channels: process from any origin, normalize remote assets
-    const incomingDms = dmChannels || [];
-    if (!isHome) {
+    // S2S DM Unification: DMs are managed exclusively by the home instance.
+    // Skip DM channels from remote origins — they're replicas served by S2S relay.
+    const incomingDms = origin === '' ? (dmChannels ?? []) : [];
+
+    // Normalize asset URLs for DMs (only relevant for home origin in practice)
+    if (origin !== '') {
       for (const dm of incomingDms) {
         for (const member of dm.members) {
           normalizeUserAssets(member, origin);
         }
       }
     }
+
     for (const dm of incomingDms) {
       channelOriginMap.set(dm.id, origin);
       if (dm.lastMessage?.id) {
         channelLastMessageIds.set(dm.id, dm.lastMessage.id);
       }
     }
+
     // Merge: remove DMs belonging to this origin from existing state, then append incoming
     const existingDmsFromOtherOrigins = get().dmChannels.filter(dm => {
       const dmOrigin = get().channelOriginMap.get(dm.id);
@@ -675,44 +670,9 @@ export const useSpaceStore = create<SpaceState>((set, get) => ({
     });
     const mergedDms = [...existingDmsFromOtherOrigins, ...incomingDms];
 
-    // Deduplicate DMs: if the same 1-on-1 conversation exists from multiple origins,
-    // prefer the home-origin copy (empty string origin = home). This handles the case
-    // where the federation relay created a local copy of a remote DM.
-    const deduplicatedDms: typeof mergedDms = [];
-    const seenPairs = new Map<string, number>(); // canonicalKey -> index in deduplicatedDms
-
-    for (const dm of mergedDms) {
-      if (dm.members.length !== 2) {
-        // Group DMs: no dedup
-        deduplicatedDms.push(dm);
-        continue;
-      }
-
-      // Build a canonical key from the two members' homeUserIds
-      const memberIds = dm.members.map(m => m.homeUserId || m.id).sort();
-      const canonicalKey = memberIds.join(':');
-      const dmOrigin = channelOriginMap.get(dm.id) ?? '';
-
-      const existingIdx = seenPairs.get(canonicalKey);
-      if (existingIdx !== undefined) {
-        // Duplicate found — keep the home-origin copy
-        const existingDm = deduplicatedDms[existingIdx]!;
-        const existingOrigin = channelOriginMap.get(existingDm.id) ?? '';
-
-        if (dmOrigin === '' && existingOrigin !== '') {
-          // New one is home, existing is remote — replace with home copy
-          deduplicatedDms[existingIdx] = dm;
-        }
-        // Otherwise keep existing (it's already home or first-seen)
-      } else {
-        seenPairs.set(canonicalKey, deduplicatedDms.length);
-        deduplicatedDms.push(dm);
-      }
-    }
-
     const update: Partial<SpaceState> = {
       spaces: mergedSpaces,
-      dmChannels: deduplicatedDms,
+      dmChannels: mergedDms,
       channelToSpaceMap,
       channelLastMessageIds,
       spacePermissions,