ci: pin npm staging smoke test to a recent rust-release run

[bolinfest]

Why

The build-test workflow stages a representative codex npm tarball by asking scripts/stage_npm_packages.py to look up a past rust-release run for a hardcoded release version. That started failing in CI because the representative version in .github/workflows/ci.yml was stale:

• the workflow was still using 0.115.0
• stage_npm_packages.py resolves native artifacts by looking for a rust-release run on the rust-v<version> branch
• that lookup no longer found a matching run for rust-v0.115.0, so the smoke test failed before it could stage the package

This PR makes that smoke test depend on a known-good recent release run instead of an older branch lookup that is no longer reliable.

What Changed

• Updated the representative release version in .github/workflows/ci.yml from 0.115.0 to 0.125.0.
• Added an explicit WORKFLOW_URL pointing at a recent successful rust-release run: https://github.com/openai/codex/actions/runs/24901475298.
• Passed that URL to scripts/stage_npm_packages.py via --workflow-url so the job can reuse the expected native artifacts directly instead of relying on gh run list --branch rust-v<version> to discover them.

That keeps the npm staging smoke test representative while making it less sensitive to older release branch history disappearing from the GitHub Actions lookup path.

Verification

• Inspected the failing CI log from build-test and confirmed the failure came from scripts/stage_npm_packages.py being unable to resolve rust-v0.115.0.
• Confirmed that https://github.com/openai/codex/actions/runs/24901475298 is a successful rust-release run for rust-v0.125.0.