feat: use download-artifact instead of manually downloading it

This should hopefully work on private repos too!

action.yml

@@ -120,6 +120,7 @@ runs:
       env:
         BASE_BRANCH: ${{ inputs.base-branch }}
         JOB_NAME: ${{ inputs.job-name }}
+        ARTIFACT_NAME: ${{ inputs.artifact-name }}
       run: |
         . "${GITHUB_ACTION_PATH}/utils.sh"
 
@@ -142,6 +143,7 @@ runs:
             '[.workflow_runs[] | select(.name == $name and .head_branch == $head_branch)] | first | .id')
 
         echo "run-id=$run_id" >> "$GITHUB_OUTPUT"
+        log Would try to download "$ARTIFACT_NAME" from "$run_id"
     - name: Download previous report
       uses: https://git.salame.cl/actions/download-artifact@d8d0a99033603453ad2255e58720b460a0555e1e # v4
       # Ensure the previous step succeeded