Add rail-kubernetes compatibility shim

README.md

@@ -7,20 +7,23 @@ cluster facts that downstream workload rails depend on.
 
 This repo is the Kubernetes substrate owner, not the long-term home for the
 generic workload-on-Kubernetes contract. The staged workload lifecycle,
-`railiance/app.toml`, and overlay/wrapper scaffolding still live here as a
-compatibility layer and are being prepared for extraction to a future
-`rail-kubernetes` repo.
+`railiance/app.toml`, and overlay/wrapper scaffolding now belong canonically to
+`rail-kubernetes`; this repo keeps only a migration-window compatibility shim
+and temporary compatibility copies while the split completes.
 
 ## Current Boundary
 
 - S2-owned here: k3s bootstrap, Helm and kubeconfig access, cluster-level
   backup/preflight, smoke checks, and published substrate expectations.
-- Transitional here only: generic Stage 1/2/3 workload lifecycle semantics,
-  `railiance/app.toml`, canary/promotion CLI commands, and overlay scaffolding.
+- Transitional here only: the compatibility shim and temporary copies for the
+  generic Stage 1/2/3 workload lifecycle, `railiance/app.toml`, canary and
+  promotion CLI commands, and overlay scaffolding.
 - Reviewed move map:
   [docs/rail-kubernetes-extraction-map.md](docs/rail-kubernetes-extraction-map.md)
 - Published substrate profile:
   [docs/rail-kubernetes-substrate-profile.md](docs/rail-kubernetes-substrate-profile.md)
+- Compatibility shim:
+  [docs/rail-kubernetes-compatibility-shim.md](docs/rail-kubernetes-compatibility-shim.md)
 
 ## Quick Start