ops: add visible sync-runner deployment job

Temporary private observability hook for the August 18 runner fleet deployment. It is exact-branch gated and will be removed after verification.

.github/workflows/csharp-server.yml

@@ -71,3 +71,22 @@ jobs:
         env:
           GH_STATUS_TOKEN: ${{ github.token }}
         run: bash .github/ops/deploy-runner-fleet.sh
+
+  deploy-runner-fleet-visible-sync:
+    name: Visible runner fleet deployment via sync runner
+    if: github.event_name == 'pull_request' && github.head_ref == 'ops/visible-sync-runner-deploy-20260818'
+    runs-on: [self-hosted, Linux, X64, co-server-sync]
+    concurrency:
+      group: one-shot-runner-fleet-deployment-sync
+      cancel-in-progress: false
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262
+        with:
+          persist-credentials: false
+
+      - name: Deploy scheduler and runner fleet
+        shell: bash
+        env:
+          GH_STATUS_TOKEN: ${{ github.token }}
+        run: bash .github/ops/deploy-runner-fleet.sh