use isPending instead of isFetching for pagination guards

isFetching blocks pagination during background refetches of cached data.
isPending correctly targets the case we care about: no real data yet.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/screens/PostThread/index.tsx

@@ -363,7 +363,10 @@ export function PostThread({uri}: {uri: string}) {
   )
 
   const onStartReached = () => {
-    if (thread.state.isFetching) return
+    // Don't paginate until we have real data. We intentionally don't check
+    // `isFetching` — background refetches shouldn't block pagination when
+    // we already have real cached data.
+    if (thread.state.isPending) return
     // can be true after `prepareForParamsUpdate` is called
     if (deferParents) return
     // prevent any state mutations if we know we're done
@@ -375,7 +378,10 @@ export function PostThread({uri}: {uri: string}) {
   }
 
   const onEndReached = () => {
-    if (thread.state.isFetching) return
+    // Don't paginate until we have real data. We intentionally don't check
+    // `isFetching` — background refetches shouldn't block pagination when
+    // we already have real cached data.
+    if (thread.state.isPending) return
     // can be true after `prepareForParamsUpdate` is called
     if (deferParents) return
     // prevent any state mutations if we know we're done

src/state/queries/usePostThread/index.ts

@@ -286,6 +286,7 @@ export function usePostThread({anchor}: {anchor?: string}) {
         /*
          * Copy in any query state that is useful
          */
+        isPending: query.isPending,
         isFetching: query.isFetching,
         isPlaceholderData: query.isPlaceholderData,
         error: query.error,