Reapply "fix(app): more startup efficiency (#18985)"

This reverts commit cbe1337f24.

packages/app/src/pages/home.tsx

@@ -113,6 +113,14 @@ export default function Home() {
             </ul>
           </div>
         </Match>
+        <Match when={!sync.ready}>
+          <div class="mt-30 mx-auto flex flex-col items-center gap-3">
+            <div class="text-12-regular text-text-weak">{language.t("common.loading")}</div>
+            <Button class="px-3" onClick={chooseProject}>
+              {language.t("command.project.open")}
+            </Button>
+          </div>
+        </Match>
         <Match when={true}>
           <div class="mt-30 mx-auto flex flex-col items-center gap-3">
             <Icon name="folder-add-left" size="large" />

packages/app/src/pages/session.tsx

@@ -1184,8 +1184,6 @@ export default function Page() {
     on(
       () => sdk.directory,
       () => {
-        void file.tree.list("")
-
         const tab = activeFileTab()
         if (!tab) return
         const path = file.pathFromTab(tab)
@@ -1640,6 +1638,9 @@ export default function Page() {
     sessionID: () => params.id,
     messagesReady,
     visibleUserMessages,
+    historyMore,
+    historyLoading,
+    loadMore: (sessionID) => sync.session.history.loadMore(sessionID),
     turnStart: historyWindow.turnStart,
     currentMessageId: () => store.messageId,
     pendingMessage: () => ui.pendingMessage,
@@ -1711,7 +1712,7 @@ export default function Page() {
           <div class="flex-1 min-h-0 overflow-hidden">
             <Switch>
               <Match when={params.id}>
-                <Show when={lastUserMessage()}>
+                <Show when={messagesReady()}>
                   <MessageTimeline
                     mobileChanges={mobileChanges()}
                     mobileFallback={reviewContent({

packages/app/src/pages/session/use-session-hash-scroll.ts

@@ -8,6 +8,9 @@ export const useSessionHashScroll = (input: {
   sessionID: () => string | undefined
   messagesReady: () => boolean
   visibleUserMessages: () => UserMessage[]
+  historyMore: () => boolean
+  historyLoading: () => boolean
+  loadMore: (sessionID: string) => Promise<void>
   turnStart: () => number
   currentMessageId: () => string | undefined
   pendingMessage: () => string | undefined
@@ -181,6 +184,21 @@ export const useSessionHashScroll = (input: {
     queue(() => scrollToMessage(msg, "auto"))
   })
 
+  createEffect(() => {
+    const sessionID = input.sessionID()
+    if (!sessionID || !input.messagesReady()) return
+
+    visibleUserMessages()
+
+    let targetId = input.pendingMessage()
+    if (!targetId && !clearing) targetId = messageIdFromHash(location.hash)
+    if (!targetId) return
+    if (messageById().has(targetId)) return
+    if (!input.historyMore() || input.historyLoading()) return
+
+    void input.loadMore(sessionID)
+  })
+
   onMount(() => {
     if (typeof window !== "undefined" && "scrollRestoration" in window.history) {
       window.history.scrollRestoration = "manual"