ci: lint, type-check and test the worker and shared packages #86

Where

.github/workflows/ci.yml:38-42 type-checks only server and extension. eslint.config.js has no block for packages/worker or packages/shared (ESLint reports the worker file as ignored). The worker has no tests.

What happens

Contract drift between the worker and Express (headers, /health, sizes) reaches the default production backend without any check failing.

Fix

Add cd packages/worker && npx tsc --noEmit to CI, extend the TS ESLint block to packages/{worker,shared}/src/**/*.ts, and add a small vitest file that calls the worker's fetch(new Request(...)) directly to check sizes, CORS and Timing-Allow-Origin headers, and 404/415 responses.