Add GitHub Actions workflow for testing

Runs the test suite (debug + release, with and without serialization)
on Linux/macOS/Windows, the full suite under Miri including the
threaded stress tests, and a wasm32-unknown-unknown release build.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: bouk

.github/workflows/test.yml

@@ -0,0 +1,50 @@
+name: test
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  test:
+    name: test (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    steps:
+      - uses: actions/checkout@v7
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo test
+      - run: cargo test --features serialization
+      - run: cargo test --release --features serialization
+
+  # The tests build with tiny table and arena sizes (see src/stringcache.rs)
+  # so this exercises table growth and migration under Miri's data-race and
+  # provenance checking, including the threaded stress tests.
+  miri:
+    name: miri
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: miri
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo miri test
+
+  wasm32:
+    name: wasm32 build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: wasm32-unknown-unknown
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo build --release --target wasm32-unknown-unknown