Temporarily test C++ on GB300

Author: bdice

.github/workflows/pr.yaml

@@ -56,6 +56,7 @@ jobs:
   build-details:
     uses: rapidsai/shared-workflows/.github/workflows/compute-build-details.yaml@main
   check-nightly-ci:
+    if: false
     runs-on: ubuntu-latest
     permissions:
       actions: read
@@ -234,6 +235,7 @@ jobs:
       enable_check_generated_files: false
       ignored_pr_jobs: "telemetry-summarize conda-python-tests-integration-optional wheel-tests-integration-optional"
   cmake-tests:
+    if: false
     needs: checks
     permissions:
       actions: read
@@ -277,6 +279,8 @@ jobs:
     if: fromJSON(needs.changed-files.outputs.changed_file_groups).test_cpp
     with:
       build_type: pull-request
+      matrix_type: nightly
+      matrix_filter: map(select(.GPU == "gb300"))
       script: ci/test_cpp.sh
   conda-cpp-debug-tests:
     needs: [checks, changed-files]
@@ -288,14 +292,15 @@ jobs:
       pull-requests: read
     secrets: inherit # zizmor: ignore[secrets-inherit]
     uses: rapidsai/shared-workflows/.github/workflows/custom-job.yaml@main
-    if: fromJSON(needs.changed-files.outputs.changed_file_groups).test_cpp
+    if: false
     with:
       build_type: pull-request
       node_type: "gpu-l4-latest-1"
       arch: "amd64"
       container_image: "rapidsai/ci-conda:26.10-latest"
       script: "ci/test_cpp_debug.sh"
   conda-python-build:
+    if: false
     needs: [build-details, conda-cpp-build]
     permissions:
       actions: read
@@ -378,6 +383,7 @@ jobs:
       dry-run: true
       version-map: '{"26.04": "legacy", "26.06": "stable"}'
   wheel-build-cpp:
+    if: false
     needs: [build-details, checks]
     permissions:
       actions: read
@@ -443,6 +449,7 @@ jobs:
       build_type: pull-request
       script: ci/test_wheel_integrations.sh
   devcontainer:
+    if: false
     permissions:
       actions: read
       contents: read
@@ -471,7 +478,7 @@ jobs:
     permissions:
       actions: write
     needs: pr-builder
-    if: ${{ vars.TELEMETRY_ENABLED == 'true' && !cancelled() && github.run_attempt == '1' }}
+    if: false
     continue-on-error: true
     steps:
       - name: Telemetry summarize