feat: fix cross-instance friends list for federated users

Friends fan-out (loadFriends/loadRequests) now waits for all remote
connections to establish before querying, fixing the empty friends list
when logged into a remote instance as a federated user.

- Add _autoConnectDone wait guard to loadFriends, loadRequests, and
  loadFederatedMutuals (same pattern as discoverStore)
- Add concurrency guards to prevent thundering herd from multiple
  ready events firing simultaneous fan-outs
- Fix deduplication to use canonical identity (homeUserId ?? id)
  instead of id:origin, preventing duplicate entries for the same
  user across instances
- Auto-connect to home instance when logged in as a federated user,
  with registry entry so it appears in Connections UI
- Allow re-adding error/disconnected instances in probeInstance

packages/web/src/utils/mutuals.ts

@@ -26,6 +26,7 @@ export interface FederatedMutuals {
  * Load mutual friends and mutual spaces across all connected instances.
  * Follows the same Promise.allSettled fan-out pattern as socialStore.loadFriends().
  *
+ * - Waits for auto-connect to finish before fanning out (same guard as socialStore)
  * - Deduplicates friends by canonical identity (homeUserId ?? id)
  * - Concatenates spaces (spaces on different instances are distinct)
  * - Normalizes assets for remote-origin results
@@ -34,6 +35,23 @@ export async function loadFederatedMutuals(
   targetUserId: string,
   targetHomeUserId?: string | null,
 ): Promise<FederatedMutuals> {
+  // Wait for all remote connections to establish before fanning out
+  if (!useInstanceStore.getState()._autoConnectDone) {
+    await new Promise<void>((resolve) => {
+      const unsub = useInstanceStore.subscribe((state) => {
+        if (state._autoConnectDone) {
+          unsub();
+          resolve();
+        }
+      });
+      // Double-check (race condition guard)
+      if (useInstanceStore.getState()._autoConnectDone) {
+        unsub();
+        resolve();
+      }
+    });
+  }
+
   const instances = useInstanceStore.getState().instances;
   const connectedInstances = instances.filter(i => i.status === 'connected');