Move instance from module to global scope

[skonves]

Resolves #78
Resolves #79

[Copilot]

Pull Request Overview

This PR moves the AsyncLocalStorage instance from module scope to global scope and adds an integration test to verify that context values remain unique across different usage paths.

• Moves AsyncLocalStorage instance initialization to globalThis in index.js.
• Introduces an init function and supporting constants in the intermediate library.
• Adds a new integration test to ensure unique context propagation.

Reviewed Changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated no comments.

File	Description
tests/express-test-harness.js	Adds integration test to verify unique context values when the library is used both directly and transitively.
packages/express-http-context-intermediate-library/index.js	Introduces an init function and constants for managing request IDs via middleware.
packages/express-http-context-intermediate-library/README.md	Adds instructions for publishing the library to NPM.
index.js	Shifts AsyncLocalStorage instance creation to a global scope using globalThis.

Files not reviewed (2)

• package.json: Language not supported
• packages/express-http-context-intermediate-library/package.json: Language not supported

Comments suppressed due to low confidence (2)

index.js:13

• [nitpick] Consider caching the global instance in the middleware, get, and set functions consistently to improve readability and avoid repeated global lookups.

const asyncLocalStorage = globalThis[STORAGE_KEY];

packages/express-http-context-intermediate-library/index.js:6

• [nitpick] Ensure that the naming for the request ID header constants is consistent and clearly distinguishes between the incoming header and the header set in the response, if appropriate.

const REQUEST_ID_HTTP_HEADER_NAME = "my-request-id";

[coveralls]

coverage: 100.0%. remained the same
when pulling 46ad2c3 on issue-78
into d8c1e4c on master.