CI: Linux arm64 Build nextest archive is canceled after runner shutdown on ubuntu-24.04-arm

What issue are you seeing?

The rust-ci-full Linux arm64 nextest archive job was canceled during the build.

Failed job:

https://github.com/openai/codex/actions/runs/27985265059/job/82825093802

Failed stage:

Tests — ubuntu-24.04-arm - aarch64-unknown-linux-gnu / Build nextest archive

The log indicates this is not a codex-cloud-tasks compilation error. The runner received a shutdown signal and then canceled the operation:

Compiling codex-cloud-tasks v0.0.0 (/home/runner/work/codex/codex/codex-rs/cloud-tasks)
##[error]The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.
##[error]The operation was canceled.

The job was running with:

• workflow: .github/workflows/rust-ci-full-nextest-platform.yml
• runner: ubuntu-24.04-arm
• target: aarch64-unknown-linux-gnu
• profile: ci-test
• use_sccache: true

What steps can reproduce the bug?

1. Run rust-ci-full for SHA a72433d5606984e71dc37a83a65a6f91af5c84b4, tag rust-v0.142.0.
2. Observe the job Tests — ubuntu-24.04-arm - aarch64-unknown-linux-gnu / Build nextest archive.
3. The job starts cargo nextest archive and begins compiling the Rust workspace.
4. Around the time codex-cloud-tasks is compiling, the runner receives a shutdown signal and the workflow reports The operation was canceled.

This appears to be runner resource pressure or runner instability during archive generation, not a deterministic Rust compilation failure.

What is the expected behavior?

The Linux arm64 Build nextest archive job should complete reliably, upload nextest-archive-linux-arm64, and allow the test shards to run afterward.

Additional information

Consider limiting Cargo build parallelism for the Linux arm64 nextest archive build, for example by passing this to cargo nextest archive:

--build-jobs 2

This should reduce peak resource pressure during archive generation and help avoid the ubuntu-24.04-arm runner being shutdown or canceled while compiling the workspace.