ci: pin GitHub Actions version comments to full semver

Renovate's helpers:pinGitHubActionDigestsToSemver preset reads version
comments to track updates. Major-only comments (e.g. # v6) produce
unhelpful changelog diffs like "v6 → v6". Full semver comments
(e.g. # v6.0.2) let Renovate show meaningful version changes.

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

.github/workflows/rag-evaluation.yml

@@ -97,7 +97,7 @@ jobs:
 
       - name: Upload test results
         if: always()
-        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5
+        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
         with:
           name: rag-evaluation-results
           path: |