fix(ci): extend runner-backend breaker to PR-gating standalone workflows

OpenGrep precise/full, sandbox-common-smoke, and plugin-init scaffold
validation were still pinned to Blacksmith runners outside ci.yml, so
PR checks starved during the Blacksmith outage even with
OPENCLAW_CI_RUNNER_BACKEND=github. Route them through the same breaker
expression and bound sandbox-common-smoke with a timeout.

.github/workflows/opengrep-precise-full.yml

@@ -21,7 +21,7 @@ permissions:
 jobs:
   scan:
     name: Scan full repository (precise)
-    runs-on: blacksmith-16vcpu-ubuntu-2404
+    runs-on: ${{ vars.OPENCLAW_CI_RUNNER_BACKEND == 'github' && 'ubuntu-24.04' || 'blacksmith-16vcpu-ubuntu-2404' }}
     timeout-minutes: 30
     steps:
       - name: Checkout

.github/workflows/opengrep-precise.yml

@@ -37,7 +37,7 @@ jobs:
   scan:
     name: Scan changed paths (precise)
     if: ${{ !github.event.pull_request.draft }}
-    runs-on: blacksmith-4vcpu-ubuntu-2404
+    runs-on: ${{ vars.OPENCLAW_CI_RUNNER_BACKEND == 'github' && 'ubuntu-24.04' || 'blacksmith-4vcpu-ubuntu-2404' }}
     timeout-minutes: 30
     steps:
       - name: Checkout

.github/workflows/plugin-init-scaffold-validation.yml

@@ -36,7 +36,7 @@ jobs:
   validate-provider-scaffold:
     name: Validate provider scaffold
     if: github.event_name != 'pull_request' || !github.event.pull_request.draft
-    runs-on: ${{ github.repository == 'openclaw/openclaw' && 'blacksmith-4vcpu-ubuntu-2404' || 'ubuntu-24.04' }}
+    runs-on: ${{ vars.OPENCLAW_CI_RUNNER_BACKEND == 'github' && 'ubuntu-24.04' || (github.repository == 'openclaw/openclaw' && 'blacksmith-4vcpu-ubuntu-2404' || 'ubuntu-24.04') }}
     timeout-minutes: 30
     steps:
       - name: Checkout

.github/workflows/sandbox-common-smoke.yml

@@ -27,7 +27,8 @@ env:
 jobs:
   sandbox-common-smoke:
     if: github.event_name != 'pull_request' || !github.event.pull_request.draft
-    runs-on: blacksmith-16vcpu-ubuntu-2404
+    runs-on: ${{ vars.OPENCLAW_CI_RUNNER_BACKEND == 'github' && 'ubuntu-24.04' || 'blacksmith-16vcpu-ubuntu-2404' }}
+    timeout-minutes: 45
     steps:
       - name: Checkout
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3