Replaces the GitHub Actions deploy lane with Cloudflare Workers Builds,
configured in the Cloudflare dashboard and wired to GitHub by the
Cloudflare Workers & Pages app.
- delete .github/workflows/web-deploy.yml
- drop both wrangler envs: one worker, and the branch picks the command
(deploy on main, versions upload everywhere else, so a preview URL is a
version of the same worker rather than a second one)
- collapse web:deploy:preview into web:deploy, now the manual override
- document the lane in CONTRIBUTING.md, since a reader will otherwise go
looking for the workflow file that is no longer there
The CLOUDFLARE_API_TOKEN and CLOUDFLARE_ACCOUNT_ID secrets are no longer
needed; Workers Builds mints its own token for the build. Watch paths now
include packages/editor-tokens, which site-tokens depends on and the old
workflow's filter missed.