Adds automated checks that were previously only run manually and
locally, closing the last remaining gap before dev can be merged
into main with confidence.
Runs on every push and pull request targeting dev or main:
- lint (eslint)
- format check (prettier --check)
- changeset presence check (non-blocking for now, see comment in
workflow file)
- unit tests (vitest)
- component/browser tests (vitest + playwright, via the existing
Docker test setup)
Fixes: #10
