fix(router): fix a possible deadlock in next_batch (#1731)

router/src/queue.rs

@@ -200,6 +200,10 @@ impl State {
             }
         }
 
+        // Pad prefill_token_budget to be a multiple of block size
+        let prefill_token_budget =
+            ((prefill_token_budget + self.block_size - 1) / self.block_size) * self.block_size;
+
         // Create span for this batch to add context to inference calls
         let next_batch_span = info_span!(parent: None, "batch", batch_size = tracing::field::Empty);
         next_batch_span.follows_from(&Span::current());