Switching from `node --env-file-if-exists=.env.local` to a hand-rolled
one-key reader. The previous shape loaded *all* of .env.local into the
parent's process.env before spawning the child, which broke e2e:
`scripts/serve.js:50` has a "don't clobber shell-set vars" guard that
treats anything pre-set in process.env as authoritative, and it can't
distinguish "really set by the shell" from "preloaded by --env-file".
So .env.test's `NEXT_PUBLIC_IS_PLATFORM=false` (the whole point of
scripts/generateLocalEnv.js) was silently overridden by .env.local's
`true`, the studio booted in platform mode, and every e2e test
auth-redirected.
The dispatcher only needs one var (STUDIO_FRAMEWORK) to pick a script.
The downstream tools (vite for build/dev, scripts/serve.js for start)
load `.env` files themselves with the correct precedence.
The top-level dev/build/start scripts now run scripts/dispatch.js, which
loads .env.local via node --env-file-if-exists and execs either the
:next or :tanstack variant based on STUDIO_FRAMEWORK. Locally the env
var lives in apps/studio/.env.local (gitignored) so the developer's
machine opts into TanStack; Vercel's Next.js prod project leaves it
unset and gets the next path. Adds :tanstack variants alongside the
existing :next ones for explicit selection.
Alaister Young