fix(client): load all available threads instead of first 50

The client was requesting only 50 threads from the server, but the
server fetches up to 500 from the Amp API. This meant users with many
threads only saw ~42 entries (50 minus stacked children), and deleting
a thread appeared to have no effect on the count because a previously-
hidden thread would backfill into the 50-thread window.

Now requests limit=500 to match the server's Amp API cap, showing all
available threads. The Amp API hard-caps at 500 — no pagination support
— so this is the maximum we can display.

Co-authored-by: Amp <amp@ampcode.com>

Author: jom-sq

src/hooks/useThreads.ts

@@ -42,7 +42,7 @@ export function useThreads() {
       try {
         const cursor = append ? cursorRef.current : null;
         const data = await apiGet<ThreadsResult>(
-          `/api/threads?limit=50${cursor ? `&cursor=${cursor}` : ''}`,
+          `/api/threads?limit=500${cursor ? `&cursor=${cursor}` : ''}`,
         );
 
         const filtered = filterDeleted(data.threads);