Merge pull request 'docs(readme): say how to get a sidecar before explaining how it is used' (#120) from docs/installer-first-setup into main

Reviewed-on: #120
Reviewed-by: Colby Whitlock <whitlocktech@gmail.com>

README.md

@@ -416,6 +416,29 @@ exposes a small, authenticated HTTP + WebSocket API; this website is a *client*
 itself is never exposed to the internet — only the sidecar is, and only the website's backend talks
 to it.
 
+### Setting up the shard side
+
+You do not build or place any of it by hand. The
+**[Runic Gateway installer](https://gitea.whitlocktech.com/RunicGateway/installer)** runs on the
+shard host, deploys the ServUO plugin and the uo-link sidecar as a matched, protocol-checked pair,
+registers the sidecar as a service, and ends by printing the four values this site needs:
+
+```
+Base URL          http://<shard-host>:8080
+WebSocket URL     ws://<shard-host>:8080/ws
+Protocol version  3
+Auth token        4f9c…
+```
+
+Paste them into **Admin → Shard** here and the bridge is live. The operator guide is
+[installer/INSTALL.md](https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/installer/INSTALL.md);
+its [Appendix A](https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/installer/INSTALL.md#appendix-a--installing-by-hand)
+is the same deployment done by hand, still supported, for a host that cannot run the binary or a
+developer working from a source tree.
+
+Nothing here needs the shard to exist: with no sidecar configured the site renders normally and
+shows the shard offline.
+
 ### How it works
 
 ```