refactor(release): separate GCP image deployment (#11108)

Author: mergify[bot]

.github/workflows/README.md

@@ -59,6 +59,7 @@ graph TB
     FindDisks[zfnd-find-cached-disks.yml]
     Deploy[zfnd-deploy-integration-tests-gcp.yml]
     DeployNodes[zfnd-deploy-nodes-gcp.yml]
+    DeployPrebuilt[zfnd-deploy-prebuilt-nodes-gcp.yml]
     Cleanup[zfnd-delete-gcp-resources.yml]
   end
 
@@ -75,6 +76,8 @@ graph TB
   PrepareBinaries --> AttachBinaries
   BuildDocker --> IT
   IT --> FindDisks --> Deploy
+  DeployNodes --> BuildDocker
+  DeployNodes --> DeployPrebuilt
 
   %% Styling
   classDef primary fill:#2374ab,stroke:#2374ab,color:white
@@ -83,7 +86,7 @@ graph TB
   class BuildDocker,PrepareBinaries,AttachBinaries primary
   class ReleaseWorkflow,ReleaseBinaries primary
   class Unit,Lint,Coverage,DockerCfg,CrateBuild,PRGate,Docs,Security secondary
-  class IT,FindDisks,Deploy,DeployNodes,Cleanup secondary
+  class IT,FindDisks,Deploy,DeployNodes,DeployPrebuilt,Cleanup secondary
   class PR,Push,ReleaseEvent,Schedule,Manual trigger
 ```
 
@@ -207,7 +210,8 @@ gh api 'repos/ZcashFoundation/zebra/actions/caches?per_page=100' \
 - **Attach release binaries** (`zfnd-attach-release-binaries.yml`): Attaches the prepared binary bundle to an existing GitHub Release
 - **Find cached disks** (`zfnd-find-cached-disks.yml`): Discovers GCP disks for stateful tests
 - **Deploy integration tests** (`zfnd-deploy-integration-tests-gcp.yml`): Orchestrates GCP VMs and test runs
-- **Deploy nodes** (`zfnd-deploy-nodes-gcp.yml`): Provision long-lived nodes
+- **Deploy nodes** (`zfnd-deploy-nodes-gcp.yml`): Build the event-specific image and orchestrate long-lived node deployment
+- **Deploy prebuilt nodes** (`zfnd-deploy-prebuilt-nodes-gcp.yml`): Deploy an explicit immutable GAR image identity
 - **Delete GCP resources** (`zfnd-delete-gcp-resources.yml`): Cleanup utilities
 - Helper scripts in `.github/workflows/scripts/` used by the above