T-0.1 Flux GitOps layout + dev/prod overlays + platform component skeletons (R-GITOPS-01/03, R-ENV-02, R-PLAT-01)

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

platform/longhorn/README.md

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+# platform/longhorn
+
+**Longhorn** — distributed replicated block storage across the 3 nodes.
+
+- **Governing ADR:** [ADR-0003 — Distributed storage: Longhorn (+ bulk tier + Velero)](../../../home-network-k3s/decisions/adr-0003-storage-longhorn.md)
+- **Spec:** [docs/04 — Storage & State](../../../home-network-k3s/docs/04-storage-and-state.md)
+- **Serves:** R-STATE-01..04
+- **Owner:** WS-STORAGE
+
+## What this stub is
+
+Flux `HelmRelease` + two `StorageClass`es:
+- **`longhorn`** — the **default**, **3-replica** replicated class (replica count is the
+  `${LONGHORN_DEFAULT_REPLICA_COUNT}` overlay knob). Durable home for app/config state and KubeVirt
+  VM disks (via CDI).
+- **`bulk`** — non-replicated tier for large media (Plex library, download staging). **STUB**: its
+  backing store is **OQ-2 (unresolved)** — escalate before finalizing. Plex's metadata DB stays on
+  the 3-replica class regardless (ADR-0003).
+
+## Contract (consumed by everyone with state)
+
+Per `roadmap/workstreams.md`, WS-STORAGE exposes the `longhorn` (replicated) and `bulk` (media)
+StorageClasses; WS-APPS/WS-VM/WS-OBS reference them from ServiceDefinitions. Do not place bulk media
+on the replicated tier or app DBs on the bulk tier.
+
+## TODO (later phases)
+
+- **OQ-2 (human):** decide the bulk-tier backing (NAS/NFS vs dedicated disk). Blocks `bulk` finalize.
+- **Phase 2 (WS-STORAGE):** dedicated Longhorn data disk path (docs/02); prove a PVC survives
+  pod destroy/rebuild (R-STATE-01, Phase-2 exit gate).
+- **Phase 4 (WS-STORAGE):** wire off-cluster backup target with Velero (R-STATE-03).