refactor(desktop): extract community destination restore hook

AppShell.tsx crossed the 1000-line desktop ratchet again after the
forward-history wiring. Move the community destination restore effect
into its own hook alongside useCommunityNavigationTransitions instead of
squeezing the call site further.

Signed-off-by: Matt Toohey <contact@matttoohey.com>

desktop/src/app/AppShell.tsx

@@ -15,6 +15,7 @@ import {
 import { useAppNavigation } from "@/app/navigation/useAppNavigation";
 import { describeHistoryLocation } from "@/app/navigation/navigationHistory";
 import { useBackForwardControls } from "@/app/navigation/useBackForwardControls";
+import { useCommunityDestinationRestore } from "@/app/useCommunityDestinationRestore";
 import { useCommunityNavigationTransitions } from "@/app/useCommunityNavigationTransitions";
 import { useLiveHomeFeedActions } from "@/app/useLiveHomeFeedActions";
 import { useChannelBrowserDialog } from "@/app/useChannelBrowserDialog";
@@ -82,11 +83,6 @@ import { CommunityRail } from "@/features/sidebar/ui/CommunityRail";
 import { useChannelMutes } from "@/features/sidebar/lib/useChannelMutes";
 import { useChannelStars } from "@/features/sidebar/lib/useChannelStars";
 import { useCommunities } from "@/features/communities/useCommunities";
-import {
-  consumePendingCommunityRestore,
-  loadCommunityDestination,
-  saveCommunityDestination,
-} from "@/features/communities/communityNavigationStorage";
 import { useAddCommunityDialogState } from "@/features/communities/addCommunityPrefill";
 import { useApplyTemplate } from "@/features/channel-templates/useApplyTemplate";
 import { relayClient } from "@/shared/api/relayClient";
@@ -276,54 +272,15 @@ export function AppShell() {
       ),
     [huddleBackingChannelIds, memberChannels, revealedHuddleChannelIds],
   );
-  const hasRestoredCommunityDestinationRef = React.useRef(false);
-  React.useEffect(() => {
-    const activeCommunityId = communitiesHook.activeCommunity?.id;
-    if (
-      hasRestoredCommunityDestinationRef.current ||
-      !channelsQuery.isSuccess ||
-      channelsQuery.dataUpdatedAt === 0 ||
-      !activeCommunityId
-    ) {
-      return;
-    }
-    hasRestoredCommunityDestinationRef.current = true;
-
-    // Restoration belongs to an explicit community transition. Cold boot and
-    // reconnect remounts must preserve the route the user explicitly opened.
-    if (!consumePendingCommunityRestore(activeCommunityId)) {
-      return;
-    }
-
-    const destination = loadCommunityDestination(activeCommunityId);
-    if (!destination || destination.kind === "home") {
-      return;
-    }
-
-    const channelIsAvailable = sidebarChannels.some(
-      (channel) => channel.id === destination.channelId,
-    );
-    if (!channelIsAvailable) {
-      saveCommunityDestination(activeCommunityId, { kind: "home" });
-      void goHome({ replace: true });
-      return;
-    }
-
-    // The normal switch path writes the remembered channel into the hash before
-    // the target community mounts, so no intermediate Inbox frame is painted.
-    // Older transition callers may still arrive at neutral Home; repair those.
-    if (selectedView === "home") {
-      void goChannel(destination.channelId, { replace: true });
-    }
-  }, [
-    channelsQuery.dataUpdatedAt,
-    channelsQuery.isSuccess,
-    communitiesHook.activeCommunity?.id,
+  useCommunityDestinationRestore({
+    activeCommunityId: communitiesHook.activeCommunity?.id,
+    channelsDataUpdatedAt: channelsQuery.dataUpdatedAt,
+    channelsLoaded: channelsQuery.isSuccess,
     goChannel,
     goHome,
     selectedView,
     sidebarChannels,
-  ]);
+  });
   const [terminalContextOverride, setTerminalContextOverride] =
     React.useState<TerminalContextOverride | null>(null);
   const { activeChannel, terminalContext } = useTerminalContext({

desktop/src/app/useCommunityDestinationRestore.ts

@@ -0,0 +1,83 @@
+import * as React from "react";
+
+import type { deriveShellRoute } from "@/app/AppShell.helpers";
+import type { useAppNavigation } from "@/app/navigation/useAppNavigation";
+import {
+  consumePendingCommunityRestore,
+  loadCommunityDestination,
+  saveCommunityDestination,
+} from "@/features/communities/communityNavigationStorage";
+import type { Channel } from "@/shared/api/types";
+
+type ShellRoute = ReturnType<typeof deriveShellRoute>;
+type AppNavigation = ReturnType<typeof useAppNavigation>;
+
+/**
+ * Restores the channel a community was last viewed on, once for the first
+ * successful channel load after an explicit community transition.
+ */
+export function useCommunityDestinationRestore({
+  activeCommunityId,
+  channelsDataUpdatedAt,
+  channelsLoaded,
+  goChannel,
+  goHome,
+  selectedView,
+  sidebarChannels,
+}: {
+  activeCommunityId: string | undefined;
+  channelsDataUpdatedAt: number;
+  channelsLoaded: boolean;
+  goChannel: AppNavigation["goChannel"];
+  goHome: AppNavigation["goHome"];
+  selectedView: ShellRoute["selectedView"];
+  sidebarChannels: Channel[];
+}) {
+  const hasRestoredCommunityDestinationRef = React.useRef(false);
+  React.useEffect(() => {
+    if (
+      hasRestoredCommunityDestinationRef.current ||
+      !channelsLoaded ||
+      channelsDataUpdatedAt === 0 ||
+      !activeCommunityId
+    ) {
+      return;
+    }
+    hasRestoredCommunityDestinationRef.current = true;
+
+    // Restoration belongs to an explicit community transition. Cold boot and
+    // reconnect remounts must preserve the route the user explicitly opened.
+    if (!consumePendingCommunityRestore(activeCommunityId)) {
+      return;
+    }
+
+    const destination = loadCommunityDestination(activeCommunityId);
+    if (!destination || destination.kind === "home") {
+      return;
+    }
+
+    const channelIsAvailable = sidebarChannels.some(
+      (channel) => channel.id === destination.channelId,
+    );
+    if (!channelIsAvailable) {
+      saveCommunityDestination(activeCommunityId, { kind: "home" });
+      void goHome({ replace: true });
+      return;
+    }
+
+    // The normal switch path writes the remembered channel into the hash before
+    // the target community mounts, so no intermediate Inbox frame is painted.
+    // Older transition callers may still arrive at neutral Home; repair those.
+    if (selectedView === "home") {
+      void goChannel(destination.channelId, { replace: true });
+    }
+  }, [
+    activeCommunityId,
+    channelsDataUpdatedAt,
+    channelsLoaded,
+    goChannel,
+    goHome,
+    selectedView,
+    sidebarChannels,
+  ]);
+}