feat(desktop): single-owner anchored scroll over the virtualized timeline

desktop/src/app/AppShell.tsx

@@ -79,6 +79,9 @@ import { relayClient } from "@/shared/api/relayClient";
 import { useIdentityQuery } from "@/shared/api/hooks";
 import { useRelayAutoHeal } from "@/shared/api/useRelayAutoHeal";
 import { useDeferredStartup } from "@/shared/hooks/useDeferredStartup";
+import { preloadAgentsScreen } from "@/app/routes/agents";
+import { preloadChannelRouteScreen } from "@/app/routes/channels.$channelId";
+import { preloadChannelViews } from "@/features/channels/ui/ChannelScreenLazyViews";
 import { joinChannel } from "@/shared/api/tauri";
 import type { Channel, RelayEvent, SearchHit } from "@/shared/api/types";
 import { ChannelNavigationProvider } from "@/shared/context/ChannelNavigationContext";
@@ -567,6 +570,19 @@ export function AppShell() {
     };
   }, []);
 
+  // Warm the lazy route chunks (channel timeline, forum, agents) once the shell
+  // is idle, so the FIRST main-nav transition doesn't stall on a cold chunk
+  // fetch+parse. `startupReady` is the existing idle-or-timeout gate; the chunk
+  // imports dedupe, so racing an actual navigation is harmless.
+  React.useEffect(() => {
+    if (!startupReady) {
+      return;
+    }
+    preloadChannelRouteScreen();
+    preloadChannelViews();
+    preloadAgentsScreen();
+  }, [startupReady]);
+
   React.useEffect(() => {
     const numericCount =
       unreadChannelNotificationCount + homeBadgeCountExcludingHighPriority;

desktop/src/app/routes/agents.tsx

@@ -3,11 +3,27 @@ import { createFileRoute } from "@tanstack/react-router";
 
 import { ViewLoadingFallback } from "@/shared/ui/ViewLoadingFallback";
 
+// The chunk import is hoisted so it can be triggered eagerly (route preload)
+// as well as lazily on render — calling it twice is a no-op, the module loader
+// dedupes and caches the in-flight promise.
+const importAgentsScreen = () => import("@/features/agents/ui/AgentsScreen");
+
 const AgentsScreen = React.lazy(async () => {
-  const module = await import("@/features/agents/ui/AgentsScreen");
+  const module = await importAgentsScreen();
   return { default: module.AgentsScreen };
 });
 
+// AgentsScreen wraps a SECOND lazy boundary (AgentsView), so warming the route
+// chunk alone still leaves AgentsView cold on first navigation. Warm both. The
+// dynamic import() keeps AgentsView in its own chunk; the loader dedupes
+// against AgentsScreen's own lazy import of the same module.
+/** Warms the AgentsScreen route chunk (and its inner AgentsView) so first
+ *  navigation doesn't stall. */
+export function preloadAgentsScreen(): void {
+  void importAgentsScreen();
+  void import("@/features/agents/ui/AgentsView");
+}
+
 export const Route = createFileRoute("/agents")({
   component: AgentsRouteComponent,
 });

desktop/src/app/routes/channels.$channelId.tsx

@@ -38,11 +38,20 @@ export const Route = createFileRoute("/channels/$channelId")({
   component: ChannelRouteComponent,
 });
 
+// Hoisted so the chunk can be warmed eagerly (route preload) as well as loaded
+// lazily on render; the loader dedupes repeat calls.
+const importChannelRouteScreen = () => import("./ChannelRouteScreen");
+
 const ChannelRouteScreen = React.lazy(async () => {
-  const module = await import("./ChannelRouteScreen");
+  const module = await importChannelRouteScreen();
   return { default: module.ChannelRouteScreen };
 });
 
+/** Warms the ChannelRouteScreen chunk so first channel open doesn't stall. */
+export function preloadChannelRouteScreen(): void {
+  void importChannelRouteScreen();
+}
+
 function ChannelRouteComponent() {
   const { channelId } = Route.useParams();
   const search = Route.useSearch();