Add native GNS server bridge

.github/workflows/gns-transport.yml

@@ -0,0 +1,46 @@
+name: GNS Transport Bridge
+
+on:
+  push:
+    paths:
+      - "server/native_transport/**"
+      - ".github/workflows/gns-transport.yml"
+  pull_request:
+    paths:
+      - "server/native_transport/**"
+      - ".github/workflows/gns-transport.yml"
+
+jobs:
+  linux:
+    name: Linux native GNS bridge
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install build dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y cmake ninja-build libssl-dev libprotobuf-dev protobuf-compiler
+
+      - name: Fetch pinned GameNetworkingSockets
+        run: |
+          GNS_SHA=f4525e39ee10f6b45181fd92d01fee75f7d71756
+          rm -rf /tmp/co-gns-src
+          git init /tmp/co-gns-src
+          git -C /tmp/co-gns-src remote add origin https://github.com/ValveSoftware/GameNetworkingSockets.git
+          git -C /tmp/co-gns-src fetch --depth 1 origin "$GNS_SHA"
+          git -C /tmp/co-gns-src checkout --detach FETCH_HEAD
+          test "$(git -C /tmp/co-gns-src rev-parse HEAD)" = "$GNS_SHA"
+
+      - name: Build and run native bridge test
+        run: |
+          cmake -S server/native_transport -B /tmp/co-server-gns-build -G Ninja \
+            -DGNS_SOURCE_DIR=/tmp/co-gns-src \
+            -DCMAKE_BUILD_TYPE=Release
+          cmake --build /tmp/co-server-gns-build --target co-gns-server-bridge-tests -j2
+          ctest --test-dir /tmp/co-server-gns-build --output-on-failure
+
+      - name: Confirm shared bridge artifact
+        run: |
+          test -f /tmp/co-server-gns-build/libcommonwealth_online_gns_bridge.so
+          ldd /tmp/co-server-gns-build/libcommonwealth_online_gns_bridge.so