fix(vite): type generated refs by their picked exports

[everton-dgn]

With fileRoutes({ types: true }), every ref is typed as the full source module even though it selects only some exports. For a route like this:

export const route = { info: { title: "Home" } };
export default () => null;

The generated type rejects routes[0].$component.import = async () => ({ default: () => null }) because route is missing. It also accepts routes[0].$$route.require().default, which is absent at runtime.

Each ref is now typed as Pick<M, Extract<P, keyof M>>, where M is the source module and P comes from ref.pick without the synthetic $css name. This covers lazy and eager refs, including server pages. The $HEAD fallback picks GET. Picked names remain accessible as any when TypeScript has no types for a JavaScript route. Markdown modules keep generic refs; refs with no names left after filtering also use the generic type.

The tests compile generated declarations with small consumer files. Component mocks returning only default typecheck, and reads outside the pick fail in both manifest views. They also cover .js and .jsx routes without allowJs, with code splitting on and off. The new cases failed before their fixes and now pass. pnpm test and pnpm exec tsc --noEmit pass.

The only shared file with #17 is test/vite.spec.ts, and its diff applies cleanly on top. With #17, the server loads a server page's module whole while the client still picks default; the narrower type holds for both.