OTel file exporter emits no terminal telemetry when streamed prompt mode is interrupted with SIGINT

Describe the bug

Interrupting an actively streaming non-interactive prompt with SIGINT produces no OpenTelemetry file at all. There is therefore no cancelled/error terminal chat or invoke_agent span and no partial timing/token evidence.

Affected version

GitHub Copilot CLI 1.0.83 on macOS.

Steps to reproduce

1. Enable the OTel file exporter and force content capture off.
2. Run copilot --prompt ... --stream on --model <available-model> with a synthetic prompt that produces a long response.
3. Wait until response deltas are actively streaming.
4. Send SIGINT to the Copilot process.
5. Inspect the configured file-export path.

This reproduced twice. In the second run, 153 assistant.message_delta JSON output records had arrived before SIGINT. The process exited by SIGINT and the configured telemetry file did not exist.

Expected behavior

On the first termination signal, Copilot should cancel the current inference, end active spans with a cancelled/error outcome, force-flush and shut down trace/metric exporters with a bounded timeout, and then preserve the conventional signal exit result. A second signal can remain a hard exit.

A downstream Collector cannot recover an active span that the producer never ended.

Privacy

The reproduction used only synthetic content and OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT=false. No credentials or user data are included.

首先使用 OTel file exporter 重现被中断的流式 prompt，并检查 CLI 对 SIGINT 的处理以及 OpenTelemetry exporter 的关闭路径。跟踪活动推理的取消、span 完成、force-flush 和有界的 exporter 关闭；完成的标准是第一次 SIGINT 会留下一个包含已取消或以错误结束的 terminal spans 的 telemetry 文件，以及惯例的信号退出结果。