Ship test-runner helpers for Vitest, Jest and node:test #1578

What happens

Using a container from a test runner is wired by hand each time. The global setup page in the docs shows the pattern for one shared container:

• a setup file that starts the container and stores it in a module variable
• project.provide("redisUrl", ...) and inject("redisUrl") to pass a serialisable value to the tests
• a teardown export that stops it
• a config entry pointing at the setup file

Per-file and per-test containers need their own beforeAll/afterAll pairs or await using.

Expected

Small optional packages that turn this into a declaration, for example for Vitest:

// vitest.setup.ts
export default defineContainers({
  redis: () => new RedisContainer("redis:8"),
});

// some.test.ts
const test = withContainers<typeof containers>();
test("stores a value", async ({ redis }) => {
  /* redis.connectionUrl */
});

with equivalents for Jest and node:test.

Where

New packages under packages/, outside packages/testcontainers and packages/modules.

Notes

• Java ships junit-jupiter and spock integration modules. .NET ships xUnit packages.
• A global setup runs in a different process from the tests, so only serialisable connection details can cross. That shapes the API.
• Independent of the core API work.

Dependencies

• Nothing blocks this. It can start now.