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/misc/kelder-acquisition.md

@@ -0,0 +1,20 @@
+# kelder-acquisition
+
+The media stack for the `kelder` site — a slimmer cousin of colony's
+[`jackflix`](../colony/jackflix.md).
+
+- **Source:** [`kelder/containers/acquisition/`](../../../nixos/boxes/kelder/containers/acquisition)
+  (`default.nix`, `networking.nix`)
+- **Host:** NixOS container on `kelder`
+
+## Role
+
+- **Jellyfin** for streaming (with hardware transcoding — the `jellyfin` user is
+  in the `render` group, `jellyfin-ffmpeg`).
+- **Acquisition:** Transmission, Jackett, Radarr, Sonarr.
+- Runs under the site's shared `kontent` user.
+
+## Networking
+
+- `internal` assignment (alt name `acquisition-ctr`) on the kelder container
+  network; download client networking in `networking.nix`.