next-upgrade: do not add --turbopack flag when --turbo exists in …

…`next dev` (#71730)

### Why?

1. When `next dev --turbo` existed, it added `--turbopack` since it was
looking for existing `--turbopack` only.
2. When there's no `"dev"` script found in package.json, inform the user
we weren't able to enable Turbopack for them.


- https://github.com/vercel/next.js/releases/tag/v15.0.1-canary.3

## Test Plan

### Suggest Turbopack

```
pnpm test:upgrade-fixture bin/__testfixtures__/suggest-turbopack
```

```diff
   "scripts": {
-    "dev": "next dev"
+    "dev": "next dev --turbopack"
   },
```

### Change `--turbo` to `--turbopack`

```
pnpm test:upgrade-fixture bin/__testfixtures__/change-turbo-to-turbopack
```

CLI output includes:
```
✔ Replaced "--turbo" with "--turbopack" in your dev script.
```

```diff
   "scripts": {
-    "dev": "next dev --turbo"
+    "dev": "next dev --turbopack"
   },
```

packages/next-codemod/bin/upgrade.ts

@@ -412,23 +412,34 @@ function isUsingAppDir(projectPath: string): boolean {
  */
 async function suggestTurbopack(packageJson: any): Promise<void> {
   const devScript: string = packageJson.scripts['dev']
-  if (devScript?.includes('--turbopack')) return
 
-  const responseTurbopack = await prompts(
-    {
-      type: 'confirm',
-      name: 'enable',
-      message: 'Enable Turbopack for next dev?',
-      initial: true,
-    },
-    { onCancel }
-  )
-
-  if (!responseTurbopack.enable) {
+  if (!devScript) {
+    console.log(
+      `${pc.red('⨯')} Could not find a "dev" script in your package.json.`
+    )
     return
   }
 
   if (devScript.includes('next dev')) {
+    // covers "--turbopack" as well
+    if (devScript.includes('--turbo')) {
+      return
+    }
+
+    const responseTurbopack = await prompts(
+      {
+        type: 'confirm',
+        name: 'enable',
+        message: `Enable Turbopack for ${pc.bold('next dev')}?`,
+        initial: true,
+      },
+      { onCancel }
+    )
+
+    if (!responseTurbopack.enable) {
+      return
+    }
+
     packageJson.scripts['dev'] = devScript.replace(
       'next dev',
       'next dev --turbopack'