fix: add timestamp_ms to StreamJsonAssistantEvent type, remove as any casts

Author: Nomadcxx

src/streaming/ai-sdk-parts.ts

@@ -42,7 +42,7 @@ export class StreamToAiSdkParts {
 
   handleEvent(event: StreamJsonEvent): AiSdkStreamPart[] {
     if (isAssistantText(event)) {
-      const isPartial = typeof (event as any).timestamp_ms === "number";
+      const isPartial = typeof event.timestamp_ms === "number";
       if (isPartial) {
         this.sawAssistantPartials = true;
         const text = extractText(event);
@@ -56,7 +56,7 @@ export class StreamToAiSdkParts {
     }
 
     if (isThinking(event)) {
-      const isPartial = typeof (event as any).timestamp_ms === "number";
+      const isPartial = typeof event.timestamp_ms === "number";
       if (isPartial) {
         this.sawThinkingPartials = true;
         const text = extractThinking(event);

src/streaming/openai-sse.ts

@@ -75,7 +75,7 @@ export class StreamToSseConverter {
 
   handleEvent(event: StreamJsonEvent): string[] {
     if (isAssistantText(event)) {
-      const isPartial = typeof (event as any).timestamp_ms === "number";
+      const isPartial = typeof event.timestamp_ms === "number";
       if (isPartial) {
         this.sawAssistantPartials = true;
         const text = extractText(event);
@@ -89,7 +89,7 @@ export class StreamToSseConverter {
     }
 
     if (isThinking(event)) {
-      const isPartial = typeof (event as any).timestamp_ms === "number";
+      const isPartial = typeof event.timestamp_ms === "number";
       if (isPartial) {
         this.sawThinkingPartials = true;
         const text = extractThinking(event);

src/streaming/types.ts

@@ -35,6 +35,7 @@ export type StreamJsonUserEvent = {
 export type StreamJsonAssistantEvent = {
   type: "assistant";
   timestamp?: number;
+  timestamp_ms?: number;
   session_id?: string;
   message: {
     role: "assistant";