Fix missing osdo-results artifact causing workflow failures

[Copilot]

The workflow downloads osdo-results artifact in three jobs (test-quality, security-scan, build-security) but never uploads it, causing "No artifact found" failures.

Changes

• Added artifact upload in setup job: Uploads the results directory created by setup-osdo action as osdo-results artifact with if-no-files-found: warn to handle empty directories
• Made downloads resilient: Added continue-on-error: true to all download steps to prevent workflow abortion when artifact is missing or empty

# In setup job
- name: Upload Results Directory
  uses: actions/upload-artifact@v4
  with:
    name: osdo-results
    path: ${{ steps.osdo-setup.outputs.results-dir }}
    if-no-files-found: warn

# In consuming jobs
- name: Download Results Directory
  uses: actions/download-artifact@v4
  continue-on-error: true
  with:
    name: osdo-results
    path: ${{ needs.setup.outputs.results-dir }}

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.