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.

.github/workflows/publish-host.yml

@@ -0,0 +1,51 @@
+name: Publish Host (Avalonia)
+
+# Produces self-contained, single-file Server Host binaries for Windows and
+# Linux. No .NET runtime is required on the target machine. Runs on demand and
+# on version tags; each build is uploaded as a workflow artifact.
+
+on:
+  workflow_dispatch:
+  push:
+    tags:
+      - "host-v*"
+
+jobs:
+  publish:
+    name: Publish ${{ matrix.rid }}
+    runs-on: [self-hosted, Linux, X64]
+    strategy:
+      fail-fast: false
+      matrix:
+        rid: [win-x64, linux-x64]
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-dotnet@v4
+        # The runner user cannot write to system /usr/share/dotnet; install the
+        # pinned SDK into a runner-writable, cached path instead.
+        env:
+          DOTNET_INSTALL_DIR: ${{ runner.tool_cache }}/dotnet
+        with:
+          dotnet-version: "8.0.x"
+
+      - name: Publish single-file self-contained
+        # Untrimmed on purpose: the host uses reflection-based Avalonia bindings,
+        # which the trimmer would strip.
+        run: >
+          dotnet publish host/CommonwealthOnline.Host.csproj
+          -c Release
+          -r ${{ matrix.rid }}
+          --self-contained true
+          -p:PublishSingleFile=true
+          -p:IncludeNativeLibrariesForSelfExtract=true
+          -p:DebugType=none
+          -o out/${{ matrix.rid }}
+          --nologo
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: CommonwealthOnline.Host-${{ matrix.rid }}
+          path: out/${{ matrix.rid }}/
+          if-no-files-found: error