Refactor GitHub Actions workflow to eliminate test duplication

[maxrantil]

Context

PR #59 introduces tests/installation-test.sh as a comprehensive standalone test script, but the GitHub Actions workflow duplicates this logic inline (~80 lines of duplication).

Problem

DRY Violation: Test logic exists in two places:

• tests/installation-test.sh (363 lines)
• .github/workflows/shell-quality.yml (200+ lines of equivalent logic)

Impact: Changes require updates in two places, increasing maintenance burden.

Recommended Solution

Refactor workflow to invoke the test script instead of duplicating logic:

- name: Run comprehensive installation tests
  run: ./tests/installation-test.sh "$TEMP_HOME" "$GITHUB_WORKSPACE"

- name: Upload diagnostic artifacts
  if: failure()
  uses: actions/upload-artifact@v4
  with:
    name: installation-test-diagnostics
    path: ${{ env.TEMP_HOME }}/diagnostics
    retention-days: 7

Benefits

• Single source of truth for test logic
• Easier maintenance
• Guaranteed consistency between CI and local tests

Trade-offs

• Loses GitHub Actions step-level visibility in CI logs
• Slightly harder to debug individual test failures (all in one step)

Estimated Effort

30-45 minutes

Priority

Medium - Follow-up to PR #59 after critical issues resolved

References

• Agent: architecture-designer (recommended this refactoring)
• Related: PR feat: enhance installation testing coverage (resolves #52) #59 (introduces the duplication)