Restyle the Avalonia server host and add a single-file publish workflow (#18)

Give the host a cohesive vault-terminal look: header wordmark with a live
status pill that glows green while running, sectioned configuration card with
per-field labels, a terminal-style server log, richer player rows (id, name,
address, packet counts), and a bold Start/Stop control bar. All existing
bindings are unchanged.

Add publish-host.yml to build self-contained, single-file win-x64 and
linux-x64 binaries on the self-hosted runner and upload them as artifacts,
and document the untrimmed publish commands in the host README.

host/README.md

@@ -25,7 +25,19 @@ server — a published `CommonwealthOnline.Server` executable, the framework
 
 ## Publish
 
+Self-contained, single-file builds that need no .NET runtime on the target.
+The host uses reflection-based Avalonia bindings, so publish **untrimmed**.
+
 ```
-dotnet publish host/CommonwealthOnline.Host.csproj -c Release -r win-x64 --self-contained false
-dotnet publish host/CommonwealthOnline.Host.csproj -c Release -r linux-x64 --self-contained false
+dotnet publish host/CommonwealthOnline.Host.csproj -c Release -r win-x64 \
+  --self-contained true -p:PublishSingleFile=true \
+  -p:IncludeNativeLibrariesForSelfExtract=true -o out/win-x64
+
+dotnet publish host/CommonwealthOnline.Host.csproj -c Release -r linux-x64 \
+  --self-contained true -p:PublishSingleFile=true \
+  -p:IncludeNativeLibrariesForSelfExtract=true -o out/linux-x64
 ```
+
+CI builds both runtimes and uploads them as artifacts — run the
+**Publish Host (Avalonia)** workflow (`.github/workflows/publish-host.yml`)
+manually, or push a `host-v*` tag.