Repository: storybook
Issue: [Bug]: `EISDIR: [postcss] Is a directory` after updating from `8.1.11` to `8.2.0` with Bun
Labels: bug,needs triage

### Describe the bug

With Storybook 8.2.0 or higher, and **using [Bun](https://bun.sh) as the JavaScript runtime instead of Node.js**, the Storybook server starts correctly but upon trying to load any preview it throws an error:

```
PS C:\Users\LoganDark\bunvite> bun storybook
$ bunx --bun storybook dev -p 6006 --no-open
storybook v8.2.0

info => Starting manager..
info => Starting preview..
info Using tsconfig paths for react-docgen
Re-optimizing dependencies because lockfile has changed
╭──────────────────────────────────────────────────────────────────────────────────────────╮
│                                                                                          │
│   Storybook 8.2.0 for react-vite started                                                 │
│   156 ms for manager and 911 ms for preview                                              │
│                                                                                          │
│    Local:            http://localhost:6006/                                              │
│    On your network:  http://169.254.27.237:6006/                                         │
│                                                                                          │
│   A new version (8.2.8) is available!                                                    │
│                                                                                          │
│   Upgrade now: npx storybook@latest upgrade                                              │
│                                                                                          │
│   Read full changelog: https://github.com/storybookjs/storybook/blob/main/CHANGELOG.md   │
│                                                                                          │
╰──────────────────────────────────────────────────────────────────────────────────────────╯
16585 |     path$n.dirname(nearestPackage.dir),
16586 |     packageCache
16587 |   ));
16588 | }
16589 | function loadPackageData(pkgPath) {
16590 |   const data = JSON.parse(fs__default.readFileSync(pkgPath, "utf-8"));
        ^
EISDIR: [postcss] Is a directory
   errno: -21
   code: "
      @font-face {
        font-family: 'Nunito Sans';
        font-style: normal;
        font-weight: 400;
        font-display: swap;
        src: url('./sb-common-assets/nunito-sans-regular.woff2') format('woff2');
      }

      @font-face {
        font-family: 'Nunito Sans';
        font-style: italic;
        font-weight: 400;
        font-display: swap;
        src: url('./sb-common-assets/nunito-sans-italic.woff2') format('woff2');
      }

      @font-face {
        font-family: 'Nunito Sans';
        font-style: normal;
        font-weight: 700;
        font-display: swap;
        src: url('./sb-common-assets/nunito-sans-bold.woff2') format('woff2');
      }

      @font-face {
        font-family: 'Nunito Sans';
        font-style: italic;
        font-weight: 700;
        font-display: swap;
        src: url('./sb-common-assets/nunito-sans-bold-italic.woff2') format('woff2');
      }
    "
 syscall: "read"
      fd: 3

      at readFileSync (native:1:1)
      at loadPackageData (C:\Users\LoganDark\bunvite\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:16590:39)
      at tryCleanFsResolve (C:\Users\LoganDark\bunvite\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:46292:23)
      at tryFsResolve (C:\Users\LoganDark\bunvite\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:46226:15)
      at C:\Users\LoganDark\bunvite\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:46048:19
      at resolveId (C:\Users\LoganDark\bunvite\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:45973:25)
      at C:\Users\LoganDark\bunvite\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:48919:17
      at processTicksAndRejections (unknown:12:39)
Sourcemap for "/virtual:/@storybook/builder-vite/setup-addons.js" points to missing source files
Sourcemap for "/virtual:/@storybook/builder-vite/vite-app.js" points to missing source files

Bun v1.1.26 (Windows x64)
error: script "storybook" exited with code 1
```

If I downgrade to Storybook 8.1.11, it works properly and the preview can be loaded/used (timestamps censored):

```
PS C:\Users\LoganDark\bunvite> bun storybook
$ bunx --bun storybook dev -p 6006 --no-open
@storybook/cli v8.1.11

info => Starting manager..
info => Starting preview..
info Using tsconfig paths for react-docgen
╭──────────────────────────────────────────────────────────────────────────────────────────╮
│                                                                                          │
│   Storybook 8.1.11 for react-vite started                                                │
│   160 ms for manager and 821 ms for preview                                              │
│                                                                                          │
│    Local:            http://localhost:6006/                                              │
│    On your network:  http://169.254.27.237:6006/                                         │
│                                                                                          │
│   A new version (8.2.8) is available!                                                    │
│                                                                                          │
│   Upgrade now: npx storybook@latest upgrade                                              │
│                                                                                          │
│   Read full changelog: https://github.com/storybookjs/storybook/blob/main/CHANGELOG.md   │
│                                                                                          │
╰──────────────────────────────────────────────────────────────────────────────────────────╯
X:XX:XX XM [vite] ✨ new dependencies optimized: @storybook/addon-themes
X:XX:XX XM [vite] ✨ optimized dependencies changed. reloading
```

### Reproduction link

https://github.com/LoganDark/bunstorybookrepro

### Reproduction steps

from [readme of above repository](https://github.com/LoganDark/bunstorybookrepro/blob/master/README.md)

## How to reproduce

1. Install latest Bun
2. Run `bun install`
3. Run `bun storybook`
4. Load <http://localhost:6006> in browser
5. Storybook server immediately crashes:
   ```
   16585 |     path$n.dirname(nearestPackage.dir),
   16586 |     packageCache
   16587 |   ));
   16588 | }
   16589 | function loadPackageData(pkgPath) {
   16590 |   const data = JSON.parse(fs__default.readFileSync(pkgPath, "utf-8"));
           ^
   EISDIR: [postcss] Is a directory
      errno: -21
      code: "
         @font-face {
           font-family: 'Nunito Sans';
           font-style: normal;
           font-weight: 400;
           font-display: swap;
           src: url('./sb-common-assets/nunito-sans-regular.woff2') format('woff2');
         }
   
         @font-face {
           font-family: 'Nunito Sans';
           font-style: italic;
           font-weight: 400;
           font-display: swap;
           src: url('./sb-common-assets/nunito-sans-italic.woff2') format('woff2');
         }
   
         @font-face {
           font-family: 'Nunito Sans';
           font-style: normal;
           font-weight: 700;
           font-display: swap;
           src: url('./sb-common-assets/nunito-sans-bold.woff2') format('woff2');
         }
   
         @font-face {
           font-family: 'Nunito Sans';
           font-style: italic;
           font-weight: 700;
           font-display: swap;
           src: url('./sb-common-assets/nunito-sans-bold-italic.woff2') format('woff2');
         }
       "
    syscall: "read"
         fd: 3
   
         at readFileSync (native:1:1)
         at loadPackageData (C:\Users\LoganDark\bunstorybookrepro\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:16590:39)
         at tryCleanFsResolve (C:\Users\LoganDark\bunstorybookrepro\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:46292:23)
         at tryFsResolve (C:\Users\LoganDark\bunstorybookrepro\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:46226:15)
         at C:\Users\LoganDark\bunstorybookrepro\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:46048:19
         at resolveId (C:\Users\LoganDark\bunstorybookrepro\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:45973:25)
         at C:\Users\LoganDark\bunstorybookrepro\node_modules\vite\dist\node\chunks\dep-BzOvws4Y.js:48919:17
         at processTicksAndRejections (unknown:12:39)
   Sourcemap for "/virtual:/@storybook/builder-vite/setup-addons.js" points to missing source files
   Sourcemap for "/virtual:/@storybook/builder-vite/vite-app.js" points to missing source files
   
   Bun v1.1.26 (Windows x64)
   error: script "storybook" exited with code 1
   ```

## How to fix

1. Open `package.json`
2. Change storybook version to `8.1.11`
3. Run `bun install`
4. Run `bun storybook`
5. Open <http://localhost:6006> in browser
6. Storybook server does not crash

### System
It doesn't work properly because it runs `npm` commands.

```
Storybook Environment Info:
(node:5476) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `node --trace-deprecation ...` to show where the warning was created)

  System:
    OS: Windows 11 10.0.25931
    CPU: (12) x64 12th Gen Intel(R) Core(TM) i5-12400F
  Binaries:
    Node: 22.1.0 - ~\AppData\Local\pnpm\node.EXE
    Yarn: 1.22.22 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 10.7.0 - ~\AppData\Local\pnpm\npm.CMD <----- active
    pnpm: 8.11.0 - ~\AppData\Local\pnpm\pnpm.EXE
  Browsers:
    Edge: Spartan (Visual Studio 2022 Command Prompt variables set.), Chromium (127.0.2610.3), ChromiumDev (Visual Studio 2022 Command Prompt variables set.)      
  npmPackages:
    @storybook/react: 8.2.0 => 8.1.11
    @storybook/react-vite: 8.2.0 => 8.1.11
    storybook: 8.2.0 => 8.1.11
```

Bun version is `1.1.26`, but this happens on any version of Bun