Add streaming terminal chat UX

src/model/openai.ts

@@ -37,13 +37,73 @@ export class OpenAIResponsesClient implements ModelClient {
       }))
     });
 
-    const toolCalls: ToolCall[] = response.output
-      .filter((item): item is OpenAI.Responses.ResponseFunctionToolCall => item.type === "function_call")
-      .map((item) => ({
-        id: item.call_id,
-        name: item.name,
-        arguments: item.arguments
-      }));
+    const toolCalls: ToolCall[] = response.output.flatMap((item) =>
+      item.type === "function_call"
+        ? [
+            {
+              id: item.call_id,
+              name: item.name,
+              arguments: item.arguments
+            }
+          ]
+        : []
+    );
+
+    await this.events?.emit("model.response", {
+      outputItems: response.output.length,
+      toolCalls: toolCalls.map((toolCall) => toolCall.name),
+      hasText: response.output_text.length > 0
+    });
+
+    return {
+      output: response.output,
+      outputText: response.output_text,
+      toolCalls
+    };
+  }
+
+  async respondStream(
+    input: AgentMessage[],
+    tools: ToolDefinition[],
+    onTextDelta: (delta: string) => void
+  ): Promise<ModelTurn> {
+    await this.events?.emit("model.request", {
+      model: this.model,
+      messages: input.length,
+      tools: tools.map((tool) => tool.name)
+    });
+
+    const stream = this.client.responses.stream({
+      model: this.model,
+      instructions: this.instructions,
+      input,
+      tools: tools.map((tool) => ({
+        type: "function",
+        name: tool.name,
+        description: tool.description,
+        parameters: tool.parameters,
+        strict: true
+      }))
+    });
+
+    for await (const event of stream) {
+      if (event.type === "response.output_text.delta") {
+        onTextDelta(event.delta);
+      }
+    }
+
+    const response = await stream.finalResponse();
+    const toolCalls: ToolCall[] = response.output.flatMap((item) =>
+      item.type === "function_call"
+        ? [
+            {
+              id: item.call_id,
+              name: item.name,
+              arguments: item.arguments
+            }
+          ]
+        : []
+    );
 
     await this.events?.emit("model.response", {
       outputItems: response.output.length,