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/sfh.md

@@ -0,0 +1,24 @@
+# sfh
+
+The home **NixOS container host** ("smart from home" / home services).
+
+- **Source:** [`nixos/boxes/home/palace/vms/sfh/`](../../../nixos/boxes/home/palace/vms/sfh)
+  (`default.nix`, `containers/`)
+- **Host:** VM on `palace`
+
+## Role
+
+- Runs the home NixOS containers via `my.containers.instances`, in the same way
+  `shill` does on colony.
+- Sits on the home network and connects to NVMe-oF storage (`cellar`) where
+  needed.
+
+## Containers
+
+Defined in [`sfh/containers/`](../../../nixos/boxes/home/palace/vms/sfh/containers)
+and imported from its `containers/default.nix`:
+
+| Container | Role | Docs |
+| --- | --- | --- |
+| `hass` | Home Assistant | [hass.md](hass.md) |
+| `unifi` | UniFi controller — **defined but currently commented out** of `containers/default.nix` | [unifi.md](unifi.md) |