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/hass.md

@@ -0,0 +1,18 @@
+# hass
+
+[Home Assistant](https://www.home-assistant.io/) — home automation.
+
+- **Source:** [`sfh/containers/hass.nix`](../../../nixos/boxes/home/palace/vms/sfh/containers/hass.nix)
+- **Host:** NixOS container on `sfh`
+
+## Role
+
+- Runs Home Assistant plus supporting services in the container. The `hass-cli`
+  is wired up against the local server for convenience.
+- Integrations/automations are configured here (see commit history for things
+  like the "West Wood" integration).
+
+## Networking
+
+- `internal` assignment (alt name `hass-ctr`), plus a loopback assignment
+  (`hass-ctr-lo`) used internally.