ci: disable github CI temporarily

Author: plexoos

.github/workflows/build-pull-request.yml

@@ -13,6 +13,9 @@ concurrency:
 
 jobs:
   build:
+    # Temporary guard while validating the Jenkins-backed PR workflow on the
+    # `jenkins-ci-pipeline` branch without running the normal Docker build matrix.
+    if: github.event.pull_request.head.ref != 'jenkins-ci-pipeline'
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -42,6 +45,7 @@ jobs:
           path: /tmp/star-sw-${{ env.STARENV }}.tar
 
   test:
+    if: github.event.pull_request.head.ref != 'jenkins-ci-pipeline'
     runs-on: ubuntu-latest
     needs: build
     strategy:
@@ -68,6 +72,7 @@ jobs:
                sh -c "set -e; MALLOC_CHECK_=3 $TEST_CMD 2>&1 | tee log; grep 'Run completed' log"
 
   ROOT5_test_doEvents:
+    if: github.event.pull_request.head.ref != 'jenkins-ci-pipeline'
     runs-on: ubuntu-latest
     needs: build
     strategy:
@@ -93,6 +98,7 @@ jobs:
                sh -c "set -e; $TEST_CMD 2>&1 | tee log;  grep '<StIOMaker::Finish> IO:' log"
 
   ROOT5_test_find_vertex:
+    if: github.event.pull_request.head.ref != 'jenkins-ci-pipeline'
     runs-on: ubuntu-latest
     needs: build
     strategy: