docs: Document the boxes

Add a top-level `README.md` mapping the boxes and per-machine docs under
`docs/boxes/` (grouped `colony/`, `home/`, `misc/`), one file per host, VM and
container documenting role, services and networking with source pointers.

Also point `AGENTS.md` at the new docs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/boxes/home/cellar.md

@@ -0,0 +1,39 @@
+# cellar
+
+The home storage server. Exports fast NVMe storage over the network so other
+machines (notably `castle`) can boot and run from it.
+
+- **Source:** [`nixos/boxes/home/palace/vms/cellar/`](../../../nixos/boxes/home/palace/vms/cellar)
+  (`default.nix`, `spdk.nix`)
+- **Host:** VM on `palace` (NVMe drives passed through)
+- **Deploy address:** `192.168.68.80`
+
+## Role
+
+- Runs **SPDK** ([`spdk.nix`](../../../nixos/boxes/home/palace/vms/cellar/spdk.nix)) as
+  a userspace storage target. The kernel `nvme` driver is blacklisted so SPDK can
+  drive the NVMe devices directly (attached by PCI BDF).
+- Builds a **RAID0** (`NVMeRaid`) across three NVMe drives, partitioned into three
+  namespaces, and exports each as an **NVMe-oF target over RDMA** (port 4420) on
+  the high-speed home network — one namespace per consumer:
+
+  | Namespace | NQN | Consumer |
+  | --- | --- | --- |
+  | `NVMeRaidp1` | `nqn.2016-06.io.spdk:river` | [`river`](river.md) |
+  | `NVMeRaidp2` | `nqn.2016-06.io.spdk:castle` | [`castle`](castle.md) |
+  | `NVMeRaidp3` | `nqn.2016-06.io.spdk:sfh` | [`sfh`](sfh.md) |
+
+  Each client is pinned by `hostnqn`, so `river`, `castle` and `sfh` all run their
+  storage off `cellar` over the network.
+
+## Networking
+
+- Exports on the high-speed home network (`lan-hi` / the `hi` assignment) over
+  RDMA; the SPDK target waits for that link to be online before starting.
+
+## Notes
+
+- The `ublk_*` calls in `my.spdk.debugCommands` are **only a debugging script** —
+  they let you create a local ublk block device to mount and inspect the RAID on
+  `cellar` itself. They are **not** how storage is exported to clients; that is the
+  `nvmf` config above.