ci: GitHub Actions — verify on Linux + macOS (arm/intel)

Checkout with submodule, JDK 25, Zig 0.16.0, ./mvnw verify (checkstyle +
tests + javadoc gate). Each runner builds its native lib with zig and tests
against it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

.github/workflows/ci.yml

@@ -0,0 +1,39 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    name: ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        # each runner builds its own native lib via zig and tests against it:
+        #   ubuntu-latest -> linux-x86_64, macos-14 -> osx-aarch64, macos-13 -> osx-x86_64
+        os: [ubuntu-latest, macos-14, macos-13]
+
+    steps:
+      - name: Checkout (with zstd submodule)
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Set up JDK 25
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '25'
+          cache: maven
+
+      - name: Set up Zig
+        uses: mlugg/setup-zig@v1
+        with:
+          version: 0.16.0
+
+      - name: Build, test and verify
+        run: ./mvnw -B -ntp verify