fix(agents): correct completion announce retry backoff schedule

src/agents/subagent-registry.ts

@@ -60,7 +60,10 @@ const ANNOUNCE_EXPIRY_MS = 5 * 60_000; // 5 minutes
 
 function resolveAnnounceRetryDelayMs(retryCount: number) {
   const boundedRetryCount = Math.max(0, Math.min(retryCount, 10));
-  const baseDelay = MIN_ANNOUNCE_RETRY_DELAY_MS * 2 ** boundedRetryCount;
+  // retryCount tracks completed failed attempts. The next retry delay should
+  // start at 1s for retry #1, then 2s, 4s, ...
+  const exponent = Math.max(0, boundedRetryCount - 1);
+  const baseDelay = MIN_ANNOUNCE_RETRY_DELAY_MS * 2 ** exponent;
   return Math.min(baseDelay, MAX_ANNOUNCE_RETRY_DELAY_MS);
 }