fix(consultation): ensure final response after tool completion

frontend/src/lib/stream-agent-response.ts

@@ -32,6 +32,14 @@ async function* readChunks(stream: ChunkStream): AsyncIterable<Chunk> {
 }
 type Status = "ready" | "degraded" | "blocked";
 
+export const ENSURE_FINAL_RESPONSE_FALLBACK =
+  "本次计算已完成，但暂时没有生成可展示的回答。请换一个角度提问，我会基于已完成的计算继续说明。";
+
+export function ensureFinalResponseText(output: string, contractIsReady: boolean) {
+  if (!contractIsReady || /\S/.test(output)) return null;
+  return ENSURE_FINAL_RESPONSE_FALLBACK;
+}
+
 type EventOptions = {
   runId: string;
   requestId: string;
@@ -202,6 +210,19 @@ export function streamAgentResponse(options: StreamAgentResponseOptions) {
             await consumeAttempt(controller, await options.retry());
           }
           if (!contractReady(options)) throw new Error("runtime_contract_incomplete");
+          const ensuredFinalResponse = ensureFinalResponseText(fullOutput, contractReady(options));
+          if (ensuredFinalResponse) {
+            if (options.state.steps.length < 32) {
+              options.state.steps.push({ sequence: options.state.steps.length + 1, kind: "validation", name: "ensure-final-response", status: "completed" });
+            }
+            if (!firstOutput) {
+              firstOutput = true;
+              await options.onFirstOutput?.();
+            }
+            send(controller, { type: "answer.delta", text: ensuredFinalResponse });
+            fullOutput = ensuredFinalResponse;
+            emitted = true;
+          }
           if (!/\S/.test(fullOutput)) {
             if (/\S/.test(first.held) || /\S/.test(first.attemptOutput)) throw new Error("runtime_contract_incomplete");
             throw new Error("empty_answer");