Using mergeConfig will cause the build of other packages to fail.

### Describe the bug

There are two packages A and B in the project. Package A depends on Package B, so package B needs to be built first. The following error occurred when running the command `vp -F B build`.

### Reproduction

https://github.com/Mario34/vp-run-bug-report

### Steps to reproduce

1.clone project

2.run `vp install`

3.run utils build `vp run --filter utils`

```txt
error: Failed to load task graph
* Failed to load task config file for package at "/vp-run-bug-report/apps/website"
* Failed to resolve vite config: GenericFailure, Error: Build failed with 1 error:
```

### System Info

```shell
VITE+ - The Unified Toolchain for the Web

Environment:
Version 24.16.0
Source engines.node
Source Path /Users/zhouhl/Code/vp-run-bug-report/package.json
Project Root /Users/zhouhl/Code/vp-run-bug-report

Tool Paths:
node /Users/zhouhl/.vite-plus/js_runtime/node/24.16.0/bin/node
npm /Users/zhouhl/.vite-plus/js_runtime/node/24.16.0/bin/npm
npx /Users/zhouhl/.vite-plus/js_runtime/node/24.16.0/bin/npx

Package Manager:
Name pnpm
Version 11.4.0
Source packageManager
Source Path /Users/zhouhl/Code/vp-run-bug-report/package.json
Project Root /Users/zhouhl/Code/vp-run-bug-report
Bin Path /Users/zhouhl/.vite-plus/package_manager/pnpm/11.4.0/pnpm/bin/pnpm

VITE+ - The Unified Toolchain for the Web

vp v0.1.23

Local vite-plus:
vite-plus v0.1.22

Tools:
vite v8.0.11
rolldown v1.0.0
vitest v4.1.6
oxfmt v0.48.0
oxlint v1.63.0
oxlint-tsgolint v0.22.1
tsdown v0.22.0

Environment:
Package manager pnpm v11.4.0
Node.js v24.16.0 (engines.node)
```

### Used Package Manager

pnpm

### Logs

```shell
VITE+ - The Unified Toolchain for the Web

failed to load config from /Users/zhouhl/Code/vp-run-bug-report/apps/website/vite.config.ts
[Vite+] resolve universal vite config error: Error: Build failed with 1 error:

[plugin externalize-deps]
Error: Failed to resolve entry for package "utils". The package may have incorrect main/module/exports specified in its package.json.
at packageEntryFailure (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:37962:30)
at resolvePackageEntry (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:37959:2)
at tryNodeResolve (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:37858:70)
at nodeResolveWithVite (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:38067:9)
at PluginContextImpl.handler (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:40268:18)
at plugin (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/bindingify-input-options-wZdDRbfo.mjs:1092:30)
at plugin. (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/bindingify-input-options-wZdDRbfo.mjs:1625:18)
at aggregateBindingErrorsIntoJsError (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/error-BrnLyQ-g.mjs:48:18)
at unwrapBindingResult (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/error-BrnLyQ-g.mjs:18:128)
at #build (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/rolldown-build-CNhzgsn2.mjs:3257:34)
at async bundleConfigFile (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:40318:17)
at async bundleAndLoadConfigFile (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:40226:18)
at async loadConfigFromFile (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:40195:42)
at async resolveConfig (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:39820:22)
at async resolveUniversalViteConfig (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/vite-plus@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_vite@8.0.14_@types+node_752acc04aa950ebaa464ce104aebe367/node_modules/vite-plus/dist/resolve-vite-config-C5AjksTj.js:70:18) {
errors: [Getter/Setter]
}
error: Failed to load task graph
* Failed to load task config file for package at "/Users/zhouhl/Code/vp-run-bug-report/apps/website"
* Failed to resolve vite config: GenericFailure, Error: Build failed with 1 error:

[plugin externalize-deps]
Error: Failed to resolve entry for package "utils". The package may have incorrect main/module/exports specified in its package.json.
at packageEntryFailure (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:37962:30)
at resolvePackageEntry (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:37959:2)
at tryNodeResolve (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:37858:70)
at nodeResolveWithVite (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:38067:9)
at PluginContextImpl.handler (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/chunks/node.js:40268:18)
at plugin (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/bindingify-input-options-wZdDRbfo.mjs:1092:30)
at plugin. (file:///Users/zhouhl/Code/vp-run-bug-report/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.22_@types+node@25.9.1_jiti@2.7.0_typescript@6.0.3_yaml@2.9.0/node_modules/@voidzero-dev/vite-plus-core/dist/rolldown/shared/bindingify-input-options-wZdDRbfo.mjs:1625:18)
```

### Validations

- [x] Read the [Contributing Guidelines](https://github.com/voidzero-dev/vite-plus/blob/main/CONTRIBUTING.md).
- [x] Check that there isn't [already an issue](https://github.com/voidzero-dev/vite-plus/issues) for the same bug.
- [x] Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example).