[RFC]: Consider using yarn for docs/site. #4220

Currently docs/site/ is managed with npm (package-lock.json) outside the root Yarn workspaces. Because the root package.json sets "packageManager": "[email protected]", running npm in docs/site/ requires setting COREPACK_ENABLE_STRICT=0 both locally and in CI (.github/workflows/docs.yml and .github/workflows/docs_site_preview.yml).

samples/community/ already shows how to keep a directory isolated from the root workspace (and from web_ci.yml / root yarn.lock) while still using Yarn Berry ([email protected]): it has its own package.json, yarn.lock, and .yarnrc.yml.

Proposed changes

1. Add "packageManager": "[email protected]" to docs/site/package.json.
2. Add docs/site/.yarnrc.yml with nodeLinker: node-modules (matching the root and samples/community/ configurations).
3. Replace docs/site/package-lock.json with docs/site/yarn.lock generated by yarn --cwd docs/site install.
4. Update .github/workflows/docs.yml, .github/workflows/docs_site_preview.yml, and docs/site/README.md to run yarn --cwd docs/site ... instead of npm --prefix docs/site ..., switch setup-node cache from "npm" to "yarn", and remove COREPACK_ENABLE_STRICT: "0".

Verification

1. yarn --cwd docs/site install --immutable succeeds without COREPACK_ENABLE_STRICT=0.
2. yarn --cwd docs/site test, yarn --cwd docs/site check, and yarn --cwd docs/site build pass.
3. Root yarn test:all and yarn build:all continue to exclude docs/site/.