[BYK]

Summary

• Pin pnpm 12.8.1, replace the Yarn lockfile, and preserve the undici override in pnpm-workspace.yaml.
• Update test and publish workflows to use a commit-pinned pnpm setup action, pnpm store caching, and frozen installs in every job, including the nested publish checkout.
• Update developer guidance and generated-file messages, add workflow regression tests, and include the automatically managed project knowledge files.

Validation

• CI=true pnpm install --frozen-lockfile
• pnpm test (127 tests)
• pnpm lint
• Prettier check on changed authored files (generated lockfile excluded)
• git diff --check