ci: avoid blacksmith queue for core checks

.github/workflows/ci.yml

@@ -1111,7 +1111,10 @@ jobs:
     name: ${{ matrix.check_name }}
     needs: [preflight]
     if: needs.preflight.outputs.run_checks_node_core_nondist == 'true'
-    runs-on: ${{ github.repository == 'openclaw/openclaw' && 'blacksmith-8vcpu-ubuntu-2404' || 'ubuntu-24.04' }}
+    # Keep core shards on GitHub-hosted runners. The Blacksmith pool is already
+    # occupied by build and extension shards; queueing these shards there hides
+    # actual test-speed improvements behind runner wait time.
+    runs-on: ubuntu-24.04
     timeout-minutes: 60
     strategy:
       fail-fast: false
@@ -1377,7 +1380,7 @@ jobs:
             runner: ubuntu-24.04
           - check_name: check-lint
             task: lint
-            runner: blacksmith-16vcpu-ubuntu-2404
+            runner: ubuntu-24.04
           - check_name: check-policy-guards
             task: policy-guards
             runner: ubuntu-24.04