ci(xtest): upload platform and KAS server logs as artifacts on failure

The audit-log artifact only contains audit events from tests that
reached the KAS. When a rewrap returns code=Internal before the audit
event fires, we currently have no server-side log to inspect from CI.

Upload PLATFORM_LOG_FILE and each KAS_*_LOG_FILE under server-logs-*
when the test step fails. Empty step outputs (multikas-not-supported
matrix rows) are dropped by upload-artifact; if-no-files-found:ignore
covers the all-empty case.

Author: dmihalcik-virtru

.github/workflows/xtest.yml

@@ -709,6 +709,21 @@ jobs:
           path: otdftests/xtest/test-results/audit-logs/*.log
           if-no-files-found: ignore
 
+      - name: Upload server logs on failure
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        if: failure()
+        with:
+          name: server-logs-${{ steps.artifact-name.outputs.sdk_version }}-${{ matrix.platform-tag }}
+          path: |
+            ${{ steps.run-platform.outputs.platform-log-file }}
+            ${{ steps.kas-alpha.outputs.log-file }}
+            ${{ steps.kas-beta.outputs.log-file }}
+            ${{ steps.kas-gamma.outputs.log-file }}
+            ${{ steps.kas-delta.outputs.log-file }}
+            ${{ steps.kas-km1.outputs.log-file }}
+            ${{ steps.kas-km2.outputs.log-file }}
+          if-no-files-found: ignore
+
   publish-results:
     runs-on: ubuntu-latest
     needs: xct