chore(deploy): add railiance handoff guardrails [skip ci]

deploy/railiance/secrets/README.md

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+# inter-hub Runtime Secret
+
+`inter-hub.env.sops.yaml` is the durable source for the production
+`inter-hub/inter-hub-env` Kubernetes Secret. The file is encrypted with the
+shared Railiance age recipient declared in the repo root `.sops.yaml`.
+
+Do not commit plaintext secret material. This directory ignores plaintext files
+by default; only `*.sops.yaml`, examples, docs, and helper scripts are tracked.
+
+## Create Or Refresh
+
+Use an attended operator shell with `kubectl`, `sops`, and access to the shared
+Railiance age identity:
+
+```bash
+tmp="$(mktemp)"
+trap 'rm -f "$tmp"' EXIT
+
+kubectl -n inter-hub get secret inter-hub-env -o json \
+  | python3 deploy/railiance/secrets/k8s-secret-json-to-sops-input.py \
+  > "$tmp"
+
+sops --encrypt \
+  --age age1aq8twfd78wvpra0had8cezcnj96tj4q0068edrz5jez8d6xwmflqdepsh4 \
+  "$tmp" > deploy/railiance/secrets/inter-hub.env.sops.yaml
+```
+
+Review only non-secret metadata before committing:
+
+```bash
+sops -d deploy/railiance/secrets/inter-hub.env.sops.yaml \
+  | sed -n '1,8p'
+```
+
+## Apply
+
+```bash
+sops -d deploy/railiance/secrets/inter-hub.env.sops.yaml \
+  | kubectl apply -f -
+
+kubectl rollout restart deployment/inter-hub -n inter-hub
+kubectl rollout status deployment/inter-hub -n inter-hub
+```
+
+## Expected Keys
+
+- `DATABASE_URL`
+- `IHP_SESSION_SECRET`
+- `IHP_BASEURL`
+- `PORT`
+- `IHP_ENV`