support null in reasoning (returned by openrouter sometimes)

Author: rychlis

src/schemas.ts

@@ -120,7 +120,7 @@ export interface Message {
   role: "assistant" | "user" | "system" | "function" | "tool"
   name?: string
   content: string | ContentArray | null
-  reasoning?: MessageReasoning[]
+  reasoning?: MessageReasoning[] | null
   function_call?: {
     name: string
     arguments: string

src/vercel-ai/langtail-language-model.ts

@@ -700,7 +700,7 @@ const openaiChatResponseSchema = z.object({
               data: z.string(),
             })
           ])),
-        ]).optional(),
+        ]).nullish(),
         function_call: z
           .object({
             arguments: z.string(),
@@ -780,7 +780,7 @@ const langtailChatChunksSchema = z.union([
                   data: z.string(),
                 })
               ])),
-            ]).optional(),
+            ]).nullish(),
             function_call: z
               .object({
                 name: z.string().optional(),