fix: message streaming

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

lib/Client/Protocol/ProtocolReader.php

@@ -56,16 +56,27 @@ final class ProtocolReader
         }
 
         if (str_starts_with($raw, '* ')) {
-            $parts = preg_split('/\s+/', substr($raw, 2), 2) ?: [];
-            $label = strtoupper($parts[0] ?? '');
+            // Keep the payload as a slice of the raw response. FETCH payloads can
+            // contain large message literals, so eagerly splitting here would keep
+            // a second full copy alive while the message is parsed.
+            $labelEnd = 2;
+            while (isset($raw[$labelEnd]) && !ctype_space($raw[$labelEnd])) {
+                $labelEnd++;
+            }
+            $label = strtoupper(substr($raw, 2, $labelEnd - 2));
+            $payloadOffset = $labelEnd;
+            while (isset($raw[$payloadOffset]) && ctype_space($raw[$payloadOffset])) {
+                $payloadOffset++;
+            }
             $this->logger?->debug('IMAP untagged response received: {raw}', [
                 'label' => $label,
                 'raw' => $raw,
             ]);
             return new UntaggedResponse(
                 $label,
-                $parts[1] ?? '',
+                '',
                 $raw,
+                $payloadOffset,
             );
         }
 
@@ -181,4 +192,4 @@ final class ProtocolReader
 
         return $raw;
     }
-}
+}