Add missing whatsapp converter to parameter mapper

The whatsapp input type had no converter registered, causing
"No converter for type: whatsapp" errors when executing WhatsApp
bot workflows.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bchapuis

packages/runtime/src/parameter-mapper.ts

@@ -331,6 +331,10 @@ const converters: Record<string, Converter> = {
     nodeToApi: typeValidatingNodeToApi("string"),
     apiToNode: typeValidatingApiToNode("string"),
   },
+  whatsapp: {
+    nodeToApi: typeValidatingNodeToApi("string"),
+    apiToNode: typeValidatingApiToNode("string"),
+  },
   any: {
     nodeToApi: (
       value: NodeParameterValue,