Load complete chat history when reaching the top (#2481)

* fix(chat): load older timeline history consistently

Pagination depended on scroll events, so short or compacted initial pages could never request older history. Reevaluate edge visibility as layout and history change, and standardize loading indicators on the canonical app spinner.

* fix(chat): keep older history loading reliably

Use authoritative timeline cursor progress so merged rows cannot stall pagination. Wait for bottom anchoring before evaluating the history edge, and re-arm retries on a fresh upward gesture without automatic failure loops.

packages/app/src/screens/workspace/workspace-desktop-tabs-row.tsx

@@ -1,3 +1,4 @@
+import { LoadingSpinner } from "@/components/ui/loading-spinner";
 import React, {
   useCallback,
   useEffect,
@@ -8,7 +9,6 @@ import React, {
   type SetStateAction,
 } from "react";
 import {
-  ActivityIndicator,
   Pressable,
   ScrollView,
   Text,
@@ -94,7 +94,7 @@ const DROPDOWN_WIDTH = 220;
 const LOADING_TAB_LABEL_SKELETON_WIDTH = 80;
 const DEFAULT_INLINE_ADD_BUTTON_RESERVED_WIDTH = 36;
 
-const ThemedActivityIndicator = withUnistyles(ActivityIndicator);
+const ThemedLoadingSpinner = withUnistyles(LoadingSpinner);
 const ThemedX = withUnistyles(X);
 const ThemedCopy = withUnistyles(Copy);
 const ThemedRotateCw = withUnistyles(RotateCw);
@@ -696,7 +696,7 @@ function TabChip({
                     const highlighted = closeHovered || pressed;
                     if (isClosingTab) {
                       return (
-                        <ThemedActivityIndicator
+                        <ThemedLoadingSpinner
                           size={12}
                           uniProps={highlighted ? foregroundColorMapping : mutedColorMapping}
                         />