CI follow-ups: normalize artifact metadata and reduce remaining publication/check noise

[lagergren]

PR #428 closes the core snapshot-era artifact reuse work, but a few smaller CI follow-ups remain. They are worth doing, but they are not correctness blockers for merging the validated artifact-promotion branch.

Context

• Snapshot-era downstream jobs now reuse staged artifacts instead of rebuilding them.
• Provenance validation exists for integration-test, snapshot publication, Docker, and Homebrew.
• The remaining gaps are mostly normalization, signal cleanup, and transport efficiency.

Concrete work

1. Normalize staged artifact metadata toward one shared schema across XDK ZIP, consumer Maven repo, snapshot Maven repo, and IntelliJ plugin bundles.
   • common fields should include commit, branch, run ID, workflow, version, artifact name, and either checksum or expected file list.
2. Simplify or unify the remaining artifact download/provenance helpers where that actually reduces maintenance.
   • avoid helper churn just for abstraction; only generalize where multiple workflows benefit.
3. Reduce nested generated-project GitHub Checks noise from integration tests.
   • current noisy checks include testapp, testlib, testsvc, and testmulti.
   • the repo-level signals should stay on the real workflow/job summaries and required checks.
4. Optimize staged Maven snapshot upload transport, especially the GitHub Packages leg.
   • current publication is correct, but still slower than it should be because the upload path is sequential and request-heavy.
   • likely improvement direction: bounded parallel upload of artifact files while keeping metadata publication ordered.

Acceptance criteria

• Metadata/provenance handling is easier to reason about across workflows.
• GitHub Actions UI shows fewer low-value nested checks.
• Snapshot Maven publication is measurably faster without weakening provenance or correctness.

References

• lang/doc/plans/ci-artifact-reuse-implementation-plan.md
• .github/actions/download-ci-artifact/action.yml
• .github/workflows/publish-snapshot.yml
• .github/workflows/publish-docker.yml
• .github/workflows/homebrew-update.yml
• PR Refine CI artifact promotion and IntelliJ snapshot publishing #428