ci: add GitHub Actions test workflow

Runs unit tests on push to main and PRs, with caching, concurrency
control, minimal permissions, and pinned action versions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nficano

.github/workflows/test.yml

@@ -0,0 +1,85 @@
+# CI for the ARCP Python SDK.
+#
+# Action pinning policy:
+#   - First-party `actions/*` actions are pinned to a major tag (e.g. `@v4`).
+#     GitHub controls these repos and major tags only move forward to
+#     non-breaking releases.
+#   - Third-party actions are pinned to a full commit SHA with the human-
+#     readable version in a trailing comment.
+name: test
+
+on:
+  push:
+    branches: [main]
+    paths-ignore:
+      - "**.md"
+      - "docs/**"
+      - "LICENSE"
+      - ".gitignore"
+      - ".editorconfig"
+  pull_request:
+    branches: [main]
+    paths-ignore:
+      - "**.md"
+      - "docs/**"
+      - "LICENSE"
+      - ".gitignore"
+      - ".editorconfig"
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: test (py${{ matrix.python-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # `requires-python = ">=3.13"` in pyproject.toml.
+        # Floor + latest stable. 3.13 is currently both, 3.14 is the next stable.
+        python-version: ["3.13", "3.14"]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@bd01e18f51369d5a26f1651c3cb451d3417e3bba # v6.10.0
+        with:
+          enable-cache: true
+          cache-dependency-glob: "uv.lock"
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install project
+        run: uv sync --frozen --all-extras --dev
+
+      - name: Ruff lint
+        run: uv run ruff check .
+
+      - name: Ruff format check
+        run: uv run ruff format --check .
+
+      - name: Pyright
+        run: uv run pyright
+
+      - name: Pytest
+        run: uv run pytest --junitxml=junit-${{ matrix.python-version }}.xml
+
+      - name: Upload junit XML on failure
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: junit-${{ matrix.python-version }}
+          path: junit-${{ matrix.python-version }}.xml
+          if-no-files-found: ignore