CI: Upload wheels to release artifacts and auto-create release drafts

[Copilot]

This PR extends the release workflow to automatically upload wheels to GitHub release artifacts and improves the release UX by auto-creating release drafts, addressing both the backup solution requested in #742 and the workflow enhancement requested in #622.

Changes Made

1. Created Shared Wheel Download Script

Added ci/tools/download-wheels that encapsulates the wheel downloading logic previously inline in release.yml. The script:

• Supports both individual components (cuda-core, cuda-bindings, etc.) and "all" components
• Maintains the same filtering logic to exclude cython test artifacts (*-tests patterns)
• Provides proper error handling and argument validation

2. Extended release-upload.yml Workflow

Enhanced the existing release upload workflow to optionally download and upload wheels:

• Added optional run-id and component inputs (maintains backward compatibility)
• Added conditional step that downloads wheels using the shared script and uploads them to GitHub releases
• Only executes wheel uploading when both optional inputs are provided

3. Refactored release.yml Workflow

Updated the main release workflow to leverage the new functionality:

• Modified the upload-archive job call to pass run-id and component parameters for wheel archiving
• Refactored the publish-wheels job to use the shared script instead of duplicated inline logic

4. Auto-create Release Drafts (Issue #622)

Enhanced the release workflow to improve UX by automatically creating release drafts:

• If a release draft for a given git tag already exists, proceeds normally (preserves existing behavior)
• If no release draft exists for the given tag, automatically creates one using gh release create --draft
• Updated workflow description to reflect the new auto-creation capability

Behavior

• Existing functionality preserved: Source archive uploading continues to work as before
• New wheel backup: When releasing, wheels are now automatically uploaded to GitHub release artifacts alongside the source archive
• Improved UX: No longer requires manually creating release drafts before running the workflow
• Code reuse: Both workflows share the same tested wheel downloading logic, eliminating duplication
• PyPI publishing unchanged: The existing PyPI/TestPyPI publishing flow continues to work normally

Testing

The implementation includes comprehensive testing:

• Script functionality validation with mock GitHub Actions artifacts
• Integration tests verifying workflow input/output consistency
• YAML syntax validation and shell script linting
• Backward compatibility verification

This provides the requested backup solution for publicly released wheels and improved release workflow UX while maintaining all existing functionality and following the principle of minimal, surgical changes.

Fixes #742 and addresses #622.

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[leofang]

@copilot thanks. Now that you're touching the release workflows, could you also take the opportunity to address #622? The logic should be

• if a release draft for a given git tag already exists, do nothing (status quo)
• otherwise, create a release draft (new)

[Copilot]

@copilot thanks. Now that you're touching the release workflows, could you also take the opportunity to address #622? The logic should be

• if a release draft for a given git tag already exists, do n...

Implemented auto-creation of release drafts as requested in #622. The release workflow now:

• Creates a draft release automatically if none exists for the given git tag
• Preserves existing behavior when a draft already exists
• Maintains the same validation logic for existing drafts

This improves the UX by eliminating the manual step of creating release drafts before running the workflow. Commit: 509d596

[leofang]

We'll know if this works next time we release!