docs: Document the deployment

Add a top-level README mapping the boxes and a full docs/ tree: topic
pages (architecture, networking, deployment), per-site box pages for
colony and home with containers nested under their hosts, remote and
mobile boxes, the installer, and the home switch fabric reference
(folded in from home-switches.md, with AGENTS.md and code comments
retargeted to its new home). Box pages carry marked assignment tables
that CI regenerates from nixos.allAssignments.

AGENTS.md points at the new docs and keeps its terse agent version of
the mechanics, referring to the topic pages for depth.

nixos/boxes/home/palace/vms/river.nix

@@ -20,7 +20,7 @@
       # collision, so the switches simply trunk the ISP's VLAN 10 straight through to river (PPPoE
       # runs directly on it) and PVID the ONT's untagged management port onto wan-pon-ont (140).
       # river takes .100 in the ONT's /24 (matching stream's modem-mgmt .100) to reach its web
-      # UI at 192.168.100.1. (See home-switches.md for the switch side and the multi-ONT plan.)
+      # UI at 192.168.100.1. (See docs/sites/home/switches.md for the switch side and the multi-ONT plan.)
       ontV4 = net.cidr.host 100 prefixes.ont.v4;
 
       # river is routing-common index 0; the Digiweb static IP we request via IPCP