[SIMPL-30451] Add distributed-execution service with guide and reference implementations

Canonical location for documentation, example workflows and reference service implementations covering distributed execution patterns. Covers AC1-AC4: execution-target selection, decision support, readiness checks and code-level linkage. Tightly coupled jobs and the loosely coupled subprocess transport are verified by the test suite; the Kubernetes pipes transport is implemented but not yet cluster-run and is marked as such in the guide.

Changelog: added

yaml/tightly-coupled/rbac-step-executor.yaml

@@ -0,0 +1,34 @@
+# Kubernetes RBAC required by the k8s_job_executor.
+#
+# The in_process and multiprocess executors need NONE of this - the run worker
+# does all the work itself. Only tightly_coupled_k8s_job, which creates one
+# Kubernetes Job per step, needs permission to manage Jobs and read their pods.
+#
+# Bind to the service account used by the Dagster run pods (dagster.serviceAccount.name).
+
+apiVersion: rbac.authorization.k8s.io/v1
+kind: Role
+metadata:
+  name: distributed-execution-step-runner
+  namespace: dagster
+rules:
+  - apiGroups: ["batch"]
+    resources: ["jobs", "jobs/status"]
+    verbs: ["create", "get", "list", "watch", "delete"]
+  - apiGroups: [""]
+    resources: ["pods", "pods/log", "pods/status"]
+    verbs: ["get", "list", "watch"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: RoleBinding
+metadata:
+  name: distributed-execution-step-runner
+  namespace: dagster
+subjects:
+  - kind: ServiceAccount
+    name: dagster-dev
+    namespace: dagster
+roleRef:
+  kind: Role
+  name: distributed-execution-step-runner
+  apiGroup: rbac.authorization.k8s.io