[BUG] 可观察性: 在完成的运行中,`model_chunk` 跨度中包含 `chunkType: 'tool-result'` 并导出了 `endedAt: null`

import { Agent } from '@mastra/core/agent';
import { Mastra } from '@mastra/core/mastra';
import { createTool } from '@mastra/core/tools';
import { Observability, TestExporter } from '@mastra/observability';
import { z } from 'zod';

const toolCallId = 'call-1';

function stream(parts) {
  return {
    stream: new ReadableStream({
      start(controller) {
        for (const p of parts) controller.enqueue(p);
        controller.close();
      },
    }),
  };
}

const step1 = () =>
  stream([
    { type: 'stream-start', warnings: [] },
    { type: 'response-metadata', id: 'r1', modelId: 'mock', timestamp: new Date(0) },
    { type: 'reasoning-start', id: 'reason-1' },
    { type: 'reasoning-delta', id: 'reason-1', delta: 'thinking' },
    { type: 'reasoning-end', id: 'reason-1' },
    { type: 'tool-input-start', id: toolCallId, toolName: 'echo' },
    { type: 'tool-input-delta', id: toolCallId, delta: '{"text":"hi"}' },
    { type: 'tool-input-end', id: toolCallId },
    { type: 'tool-call', toolCallId, toolName: 'echo', input: '{"text":"hi"}' },
    { type: 'finish', finishReason: 'tool-calls', usage: { inputTokens: 1, outputTokens: 1, totalTokens: 2 } },
  ]);

const step2 = () =>
  stream([
    { type: 'stream-start', warnings: [] },
    { type: 'response-metadata', id: 'r2', modelId: 'mock', timestamp: new Date(0) },
    { type: 'text-start', id: 'text-1' },
    { type: 'text-delta', id: 'text-1', delta: 'done' },
    { type: 'text-end', id: 'text-1' },
    { type: 'finish', finishReason: 'stop', usage: { inputTokens: 1, outputTokens: 1, totalTokens: 2 } },
  ]);

let call = 0;
const model = {
  specificationVersion: 'v2',
  provider: 'mock',
  modelId: 'mock-model',
  supportedUrls: {},
  async doGenerate() {
    throw new Error('not used');
  },
  async
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