[Trace] Cancelled Agent runs are rendered as running in the timeline

[Guo-Yixin]

Problem

projectTrace() preserves the overall run status as cancelled, but the corresponding run step in FolioTrace.steps only maps failed and completed. A cancelled run therefore gets status: "running" in the timeline.

This makes the trace contain contradictory observability data: the trace header says cancelled while the run step still appears active.

Expected behavior

A cancelled run should produce a run timeline step with status: "cancelled".

Reproduction

const trace = projectTrace({
  run: {
    id: 'r-cancel',
    sessionId: 's',
    status: 'cancelled',
    input: 'run',
    startedAt: 1,
    completedAt: 2,
  },
  messages: [],
});

trace.status === 'cancelled';
trace.steps.find((step) => step.kind === 'run')?.status === 'running'; // current behavior

Proposed scope

• Add cancelled to the trace step status type.
• Preserve Run.status === "cancelled" when projecting the run timeline step.
• Add a regression test.

[Guo-Yixin]

/claim

我想处理这个问题：修复 Trace 时间线将已取消 Agent run 错误显示为 running 的问题，并补充 core projection 回归测试。不改变运行时和持久化协议。

[github-actions]

@Guo-Yixin 已认领该 Issue，并已自动设为 Assignee。提交 PR 时请在描述中写 Closes #199。