CI broken — actions/upload-artifact@v3 / download-artifact@v3 are deprecated #82

.github/workflows/wheels.yml uses actions/upload-artifact@v3 and actions/download-artifact@v3, both retired by GitHub — every job now hard-fails immediately at "Set up job" on any branch, including master:

This request has been automatically failed because it uses a deprecated version of actions/upload-artifact: v3.

Deprecation notice: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

Recommend bumping straight to latest (upload-artifact@v7, download-artifact@v8) rather than the minimum v4 — no breaking changes in between for this workflow's usage. One behavior change either way: v4+ requires a unique name per upload (v3 merged same-named artifacts silently), so each matrix leg needs a distinct name, reassembled on download via pattern/merge-multiple.

PR: #83