The Flutter client (#356) needs to consume the same FabledSword tokens
the web SPA uses. Move the data into a structured tokens.json file and
generate tokens.generated.css from it on every Vite build. The Flutter
side gets its own generator pointed at the same JSON.
No visual change — generated CSS matches the previous hand-written file.
Also installs @types/node devDependency: tsconfig already declared
"types": ["node"] but no Node builtins were referenced in TS until now,
so the missing types were latent. The new vite.config.ts plugin imports
node:child_process, surfacing the gap.
bvandeusen