fix: replace DEPLOYMENT.md symlink with actual file

CI smoke test uses [ -f ] which fails on git symlinks. Replace
docs/guides/DEPLOYMENT.md (was symlink to docs/deployment/DEPLOYMENT.md)
with the real file so the CI required_files check passes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: aurelianware