fix: identify honestly to HN and retry with backoff on 419/429/5xx

The spoofed Chrome User-Agent drew HTTP 419 from HN; an honest UA gets 200.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/favorites.ts

@@ -48,16 +48,30 @@ export function parseFavorites(html: string, limit = 10): Favorite[] {
     .slice(0, limit);
 }
 
-export async function fetchFavoritesHtml(user: string): Promise<string> {
-  const resp = await fetch(`${HN}/favorites?id=${encodeURIComponent(user)}`, {
-    headers: {
-      "User-Agent":
-        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36",
-    },
-  });
+const USER_AGENT =
+  "hackernews-favs-cron/1.0 (personal homelab job; one request per week)";
+const RETRYABLE = new Set([419, 429, 500, 502, 503, 504]);
+
+/**
+ * Fetch the favorites page, identifying ourselves honestly. Retries a few
+ * times with exponential backoff on rate-limit/transient statuses, then fails
+ * loudly (the CronJob's backoffLimit takes over).
+ */
+export async function fetchFavoritesHtml(
+  user: string,
+  attempts = 4,
+  baseDelayMs = 5000,
+): Promise<string> {
+  const url = `${HN}/favorites?id=${encodeURIComponent(user)}`;
+  for (let attempt = 1; ; attempt++) {
+    const resp = await fetch(url, { headers: { "User-Agent": USER_AGENT } });
     const html = await resp.text();
-  if (!resp.ok) {
-    throw new Error(`HN responded ${resp.status}: ${html.slice(0, 300)}`);
+    if (resp.ok) return html;
+    if (!RETRYABLE.has(resp.status) || attempt >= attempts) {
+      throw new Error(
+        `HN responded ${resp.status} after ${attempt} attempt(s): ${html.slice(0, 300)}`,
+      );
+    }
+    await new Promise((r) => setTimeout(r, baseDelayMs * 2 ** (attempt - 1)));
   }
-  return html;
 }