Complete jest -> vitest migration

[trevor-scheer]

Summary

Migrates the last Jest package to vitest and removes all Jest infrastructure from the monorepo. The mechanical jest.* → vi.* port was straightforward, but fetch-mock couldn't follow — vitest's mock system doesn't intercept CJS require() calls from node_modules, so jest.mock('@whatwg-node/fetch') silently stops working. Replaced fetch-mock with MSW which intercepts at the network layer.

Changes

• Port all 10 test files from jest.* to vi.* (imports, mocks, timers, type helpers)
• Add vitest.config.mts with clearMocks, graphql dedup alias, and graphql-language-service src alias for unbundled workspace resolution
• Replace fetch-mock v6 with msw v2 for HTTP mocking in GraphQLCache.test and MessageProcessor.spec
• Remove @whatwg-node/fetch, cross-env from server devDeps (only existed for the old mock setup)
• Remove jest, ts-jest, @types/jest, @types/fetch-mock, fetch-mock, babel-plugin-macros, eslint-plugin-jest from root
• Delete jest.config.js, jest.config.base.js, trim babel.config.js env.test block
• Simplify root scripts: test → turbo run test, test:ci → yarn tsc && yarn test
• Replace eslint-plugin-jest with eslint-plugin-vitest for test lint coverage

Necessary changes due to removing Jest

@ts-expect-error on prettier subpath imports

Several files import prettier subpaths like prettier/parser-graphql. With moduleResolution: "node", TypeScript can't resolve these because it doesn't read the exports field in package.json. Previously this worked because @types/prettier@2.6.4 (a transitive dep of jest-snapshot) provided the type declarations. With jest removed, those types are gone. The proper fix is migrating to moduleResolution: "node16" or "bundler", but that's out of scope here.

jsdom added as an explicit dependency

Six packages set environment: 'jsdom' in their vitest configs. Vitest lists jsdom as an optional peer dep, so it must be installed explicitly. It was previously available as a transitive dependency of jest (jest-environment-jsdom → jsdom).

Note

The Jest Unit & Integration Tests check will need to be marked as not required in order for this to pass once it's ready to merge.

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[dimaMachina]

Suggested change

	"test:ci": "yarn tsc && yarn test",
	"test:ci": "yarn test",

do we really need run this script before tests?

[dimaMachina]

amazing improvement!