test: Docker-isolated integration test runner (#287)

CLI integration tests (contracts, content, version) now run in a Docker
container with GIT_MIND_DISABLE_UPGRADE_CHECK=1 set at the image level.
npm test runs unit tests only; npm run test:integration runs Docker.

Author: flyingrobots

test/Dockerfile

@@ -0,0 +1,27 @@
+FROM node:22-slim
+
+RUN apt-get update && apt-get install -y git python3 make g++ && rm -rf /var/lib/apt/lists/*
+
+# Disable upgrade check — no network egress in test container
+ENV GIT_MIND_DISABLE_UPGRADE_CHECK=1
+ENV NO_COLOR=1
+
+WORKDIR /app
+
+# Install deps first (layer cache)
+COPY package.json package-lock.json ./
+RUN npm ci
+
+# Copy source
+COPY bin/ bin/
+COPY src/ src/
+COPY test/ test/
+COPY docs/contracts/ docs/contracts/
+COPY extensions/ extensions/
+
+# Git identity for tests that init repos
+RUN git config --global user.email "test@test.com" && \
+    git config --global user.name "Test"
+
+# Run only integration tests (files that spawn bin/git-mind.js)
+CMD ["npx", "vitest", "run", "test/contracts.integration.test.js", "test/content.test.js", "test/version.test.js"]