fix(ai-openrouter): allow partial tool_call deltas in streaming (closes #6128) (#6131)

Author: fabstorres

.changeset/huge-peaches-jump.md

@@ -0,0 +1,5 @@
+---
+"@effect/ai-openrouter": patch
+---
+
+Allow partial tool_call deltas in OpenRouter streaming

packages/ai/openrouter/src/OpenRouterClient.ts

@@ -313,10 +313,10 @@ export class ChatStreamingMessageToolCall extends Schema.Class<ChatStreamingMess
 )({
   index: Schema.Number,
   id: Schema.optionalWith(Schema.String, { nullable: true }),
-  type: Schema.Literal("function"),
+  type: Schema.optionalWith(Schema.Literal("function"), { nullable: true }),
   function: Schema.Struct({
     name: Schema.optionalWith(Schema.String, { nullable: true }),
-    arguments: Schema.String
+    arguments: Schema.optionalWith(Schema.String, { nullable: true })
   })
 }) {}