chore: remove unrelated vercelStreamConverter changes

Per reviewer feedback — keeping this PR focused on the
system-message tools parser fix.

Author: MumuTW

packages/openai-adapters/src/test/vercelStreamConverter.test.ts

@@ -34,10 +34,7 @@ describe("convertVercelStreamPart", () => {
     const result = convertVercelStreamPart(part, options);
 
     expect(result).not.toBeNull();
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    expect((result?.choices[0].delta as any).reasoning_content).toBe(
-      "Let me think...",
-    );
+    expect(result?.choices[0].delta.content).toBe("Let me think...");
   });
 
   test("returns null for tool-call (handled by tool-input-start/delta)", () => {

packages/openai-adapters/src/vercelStreamConverter.ts

@@ -86,11 +86,8 @@ export function convertVercelStreamPart(
       });
 
     case "reasoning-delta":
-      return chatChunkFromDelta({
-        delta: {
-          // `reasoning_content` is not yet typed in OpenAI's SDK types.
-          reasoning_content: part.text,
-        } as ChatCompletionChunk.Choice["delta"],
+      return chatChunk({
+        content: part.text,
         model,
       });