Add test task to turbo.json and include it in the build-and-typecheck
job. Turbo handles the dependency graph: builds deps first, then runs
typecheck and test in parallel for each package.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Split single CI job into parallel lint + build-and-typecheck jobs.
Add turbo cache via actions/cache for faster subsequent runs.
Use single turbo invocation for build+typecheck to optimize task
scheduling. Add concurrency group to cancel stale PR runs.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>