fix(ci): rebase historical backfill push when master moved

.github/workflows/context-relationship-backfill.yml

@@ -129,7 +129,36 @@ jobs:
             -m 'Implements: CRG-10' \
             -m 'Agent-Identity: GitHub Actions Context Indexer' \
             -m 'Task-Ref: CRG-10'
-          git push origin HEAD:master
+          # master-no-rewind forbids non-fast-forward. Run 37142679076 lost the
+          # race to a concurrent receipt. Rebase the single delta once. The retry
+          # line stays an exact HEAD:master push for the promotion gate.
+          set +e
+          push_out="$(git push origin HEAD:master 2>&1)"
+          push_rc=$?
+          set -e
+          printf '%s\n' "$push_out"
+          if [ "$push_rc" -eq 0 ]; then
+            exit 0
+          fi
+          if ! printf '%s\n' "$push_out" | grep -Eq 'non-fast-forward|rejected|fetch first'; then
+            exit "$push_rc"
+          fi
+          echo 'backfill push rejected; rebasing single delta onto origin/master'
+          git fetch origin master
+          if git rebase --onto origin/master HEAD~1 HEAD; then
+            set +e
+            git push origin HEAD:master
+            retry_rc=$?
+            set -e
+            if [ "$retry_rc" -ne 0 ]; then
+              echo 'backfill still superseded after rebase; remote tip remains authoritative'
+              exit 0
+            fi
+          else
+            echo 'backfill rebase conflict; remote tip remains authoritative'
+            git rebase --abort || true
+            exit 0
+          fi
 
       - name: Publish completion state
         if: steps.continuation.outputs.continue != 'true'