`vinext start` runs the Node server for Cloudflare projects and cannot find the Worker build (init advertises it as "Start the built Worker locally with Wrangler")

## Problem

For a Cloudflare project, `vinext init` presents `start:vinext` as the way to run the built Worker locally:

```
pnpm run start:vinext Start the built Worker locally with Wrangler
```

but the script it writes is `vinext start`, which is the **Node** production server. It never invokes Wrangler, and it looks for build output that a Cloudflare build does not produce, so it fails immediately after a successful build:

```
$ vinext build
✓ built in 9.27s

$ vinext start
[vinext] No build output found in /path/to/app/dist
Run `vinext build` first.
```

`dist/` is populated — just not where the Node server looks.

## Cause

`startProdServer` (`dist/server/prod-server.js`) probes two fixed paths:

```js
const rscEntryPath = path.join(resolvedOutDir, "server", "index.js"); // App Router
const serverEntryPath = path.join(resolvedOutDir, "server", "entry.js"); // Pages Router
const isAppRouter = fs.existsSync(rscEntryPath);
if (!isAppRouter && !fs.existsSync(serverEntryPath)) {
console.error(`[vinext] No build output found in ${outDir}`);
```

With `@cloudflare/vite-plugin`, the Worker is emitted to `dist//index.js` per the plugin's convention, so neither path exists unless the Worker happens to be named `server`.

Even if the path were corrected, running a Cloudflare build under the Node server is the wrong runtime: the point of building for Workers is to exercise it on workerd, where the available APIs differ.

## Reproduction

```sh
vinext init --platform cloudflare --skip-check
vinext build
vinext start # -> "No build output found"
```

Running Wrangler directly against the emitted config does start the Worker:

```sh
wrangler dev --config dist//wrangler.json
```

## Expected

For a project configured for Cloudflare, `vinext start` runs the built Worker on workerd via Wrangler, using the emitted `dist//wrangler.json` — matching what `init` advertises. Node projects keep the current behaviour.

Detecting the platform from the presence of `@cloudflare/vite-plugin` in the Vite config (or a `wrangler.jsonc` in the project root) would let one command do the right thing for both targets. Failing that, `init` should at minimum scaffold a `start:vinext` that calls Wrangler for Cloudflare projects, and the "No build output found" message should mention the Cloudflare output location.

## Environment

- vinext `1.0.0-beta.6`
- `@cloudflare/vite-plugin`, `wrangler` `4.123.0`
- Vite `8.1.0`
- Pages Router, `vinext init --platform cloudflare`

Reproduce the issue with the listed vinext init, build, and start commands, then inspect dist/server/prod-server.js and the Cloudflare output under dist/. Verify how the generated start script and emitted dist//wrangler.json are connected; done means Cloudflare projects run the built Worker through Wrangler while Node projects retain their current start behavior.

Written by the indexing model from the issue text.