ci: require quality checks for master

[micheletriaca]

What changed

• add a single quality GitHub Actions check for pull requests and pushes to
  master
• run on Ubuntu 24.04 with Node.js 24
• install from the lockfile, run the complete lint/test suite, and build the
  production bundle
• cancel superseded runs for the same pull request
• do not run CI for tag pushes

Why

Fast-Sfdc already prevented deletion and force-pushes on the default branch,
but it did not require pull requests or CI. This workflow provides one stable
required check without duplicating the six-platform release matrix.

Validation

• npm test — 25 tests passed, including lint and type-check/build
• npm run package — production bundle completed
• git diff --check