Run the LTS test suite on ALCF GitLab CI, bridged to GitHub PRs

[michel2323]

This adds Aurora CI through ALCF's GitLab CI service while keeping GitHub as the source of truth, and retires the GitHub Actions self-hosted runner it replaces.

How it works

• The ALCF GitLab project (mschanen/oneAPI-jl) pull-mirrors this repository and runs pipelines on mirrored branches.
• .gitlab-ci.yml (ignored by GitHub CI): a three-stage Aurora pipeline. The PBS debug queue caps 1-node jobs at 1 h, so the support-library build and env instantiation/precompilation run on the login-node shell runner into a persistent depot on flare, and only the test run itself goes through PBS. The build stage devs the checkout into the test env (manifests are gitignored, and a plain instantiate would silently test the registry release) and ships test/Manifest.toml to the batch job as an artifact. The test job runs with --code-coverage=user, collapses coverage to lcov.info, and a token-gated allow_failure job uploads to Codecov against this repo's slug — the LTS-gated branches are unreachable on the rolling stack, so this is their only coverage signal.
• .github/workflows/alcf.yml: makes the GitLab pipeline visible as this PR check. Pushes to main and same-repo PRs force a pull-mirror sync and poll the pipeline for the head SHA; fork PRs run only when a maintainer applies the alcf-ci label (the workflow moves refs only and never executes PR code — the Aurora-side execution of labeled fork code is the deliberate, opt-in exception, since GitLab CI jobs run as an ALCF user).
• ci.yml removed: the self-hosted LTS job is superseded by the above; buildkite keeps covering the rolling stack.
• Docs on hosted runners: the docs build only needs modules = [oneAPI] for docstrings and has no doctests, so it moves from the self-hosted runner to ubuntu-latest with versioninfo() guarded. This keeps Documenter's native deploy (DOCUMENTER_KEY, PR previews) instead of recreating deployment from GitLab.

Validation

Iterated to green on a scratch branch of the mirror: build stage 96 s warm, full LTS suite green in ~19 min wall including PBS queue wait (pipeline 58632). The "LTS stack (ALCF GitLab CI, Aurora)" check on this PR is the same-repo bridge path exercising itself end to end; the docs check now validates the GPU-less docs build.

Uses the ALCF_GITLAB_TOKEN repo secret (GitLab project access token, api + write_repository). Codecov upload activates once a CODECOV_TOKEN CI/CD variable is set on the GitLab project.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.97%. Comparing base (4b116f1) to head (3128150).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #613      +/-   ##
==========================================
+ Coverage   78.51%   79.97%   +1.45%     
==========================================
  Files          50       50              
  Lines        3496     3496              
==========================================
+ Hits         2745     2796      +51     
+ Misses        751      700      -51     

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[michel2323]

Only the default Julia version loaded via module load julia is tested. As of now, this is 1.12.