revert: remove actions/setup directory (not needed for releases)

The actions/setup directory was added in error. Investigation showed:
- Run 21304200959 (release.yml "Build and Release") - SUCCEEDED
- Run 21304200974 (separate agentic workflow) - FAILED

The release.yml workflow succeeded without actions/setup. The failed
workflow is an unrelated org-level agentic workflow that requires
different configuration.

This reverts commits 8a493d5 and ecf69d7.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Mossaka