148b5924

By: Michael Lynch <git@mtlynch.io>

Migrate development tooling from npm to pnpm

Pin pnpm, replace the npm lockfile with pnpm-lock.yaml, and use pnpm's
fixed-output dependency fetcher and config hook for frontend and E2E Nix
targets. Run ESLint only against Git-tracked JavaScript files.

Validation: nix build .#e2e-tests and the tracked-JavaScript ESLint command
pass. build-all-flake-targets remains blocked by pre-existing Prettier drift in
four unmodified template files.