Fix: Handle non-iterable content from inner result

Co-authored-by: OskarStark <995707+OskarStark@users.noreply.github.com>

Author: Copilot

src/agent/src/Toolbox/StreamResult.php

@@ -32,13 +32,18 @@ public function getContent(): \Generator
         foreach ($this->generator as $value) {
             if ($value instanceof ToolCallResult) {
                 $innerResult = ($this->handleToolCallsCallback)($value, Message::ofAssistant($streamedResult));
-                
+
                 // Propagate metadata from inner result to this result
                 foreach ($innerResult->getMetadata()->all() as $key => $metadataValue) {
                     $this->getMetadata()->add($key, $metadataValue);
                 }
-                
-                yield from $innerResult->getContent();
+
+                $content = $innerResult->getContent();
+                if (is_iterable($content)) {
+                    yield from $content;
+                } else {
+                    yield $content;
+                }
 
                 break;
             }