ci: add GitHub Actions workflow for typecheck, build, and tests

[slegarraga]

CI: GitHub Actions workflow (typecheck + build + tests)

Closes #19.

What

A single ci.yml workflow that runs on pushes to main and on every PR, across a Node 20 and 22 matrix:

1. npm ci
2. Typecheck: npx tsc -b
3. Production build: npm run build (which itself runs tsc -b && vite build)
4. Tests: npm run --if-present test

Plus two small quality-of-life details: npm caching via actions/setup-node, and a concurrency group (${{ github.workflow }}-${{ github.ref }}, cancel-in-progress) so pushing a new commit to an open PR cancels its superseded run instead of queueing both.

Why the test step uses --if-present

There is no test script on main yet; #39 adds Vitest with "test": "vitest run". With this flag the job is fully green on main today (the step skips), and the moment #39 merges the same workflow picks up the suite with zero coordination or edits needed. I verified both sides of that bridge locally:

• On current main: npm run --if-present test exits 0 and skips.
• On the test: add Vitest runner and unit tests for generator functions #39 branch: the identical command runs Vitest, 20/20 tests pass in 2 files.

Validation

All executed locally against this exact tree before opening the PR:

• YAML parses cleanly (6 steps, single ci job).
• npx tsc -b: no errors found.
• npm run build: succeeds, bundle emitted (280 kB js / 90 kB gzip).
• npm run --if-present test on main: exit 0, skipped as designed.
• Same command on test: add Vitest runner and unit tests for generator functions #39's branch: 20 passed / 20.

The first real Actions run will confirm the hosted path once this PR opens.

[vercel]

@slegarraga is attempting to deploy a commit to the zanni098's projects Team on Vercel.

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[zanni098]

Workflow looks right — green on this PR, and it's the CI setup we want. One change before merge:

Drop Node 20 from the matrix (keep 22, optionally add 24). Once #39 lands with jsdom 30 / jest-dom 7, those need a newer Node — this PR's green runs predate that bump, so they don't prove Node 20 compatibility once both merge. If 20 stays in the matrix, main goes red as soon as both are in.

Ping me when that's pushed and I'll merge.