vpr appears not to preserve the pnpm lifecycle environment, causing npm-run-all2 to fall back to npm

### Describe the bug

In a project configured to use pnpm, running a package script through `vpr` causes `npm-run-all2` / `run-p` to invoke child scripts with npm instead of pnpm.

The same script works correctly when launched with `pnpm run`.

The project declares pnpm as its package manager. When `run-p` is launched by pnpm, it correctly uses pnpm for the child scripts. When it is launched by `vpr`, it falls back to npm, which then fails with `EBADDEVENGINES` because the project only permits pnpm.

Expected behavior:

- `vpr check` should preserve enough package-manager lifecycle environment for child process runners to detect pnpm.
- Child scripts should be executed using pnpm, consistently with `pnpm run check`.

Actual behavior:

- `pnpm run check` succeeds.
- `vpr check` causes `run-p` to invoke npm for the child scripts.
- npm fails because `devEngines.packageManager` requires pnpm.

This appears to happen because the environment provided by `vpr` differs from the environment provided by `pnpm run`, particularly package-manager lifecycle variables such as `npm_execpath`.

A serial workaround that explicitly invokes pnpm works, but it loses parallel execution. In my project, the parallel command takes 3.94 seconds, while the serial workaround takes 6.35 seconds.

### Reproduction

https://github.com/bling-yshs/vue-demo/tree/archive/vp

### Steps to reproduce

1. Clone the reproduction repository.

2. Install dependencies:

```bash
vp i
```

3. Run the parallel script directly through pnpm:

```bash
pnpm run check
```

All three child scripts complete successfully.

4. Run the same script through Vite+:

```bash
vpr check
```

5. Observe that `npm-run-all2` invokes the child scripts using npm instead of pnpm. npm then exits with `EBADDEVENGINES` because the project declares pnpm in `devEngines.packageManager`.

### System Info

```shell
D:/code/Webstorm/vue-demo
$ vp env current
VITE+ - The Unified Toolchain for the Web

Environment:
Version 24.19.0
Source .node-version
Source Path D:\code\Webstorm\vue-demo\.node-version
Project Root D:\code\Webstorm\vue-demo

Tool Paths:
node C:\Users\yshs\.vite-plus\js_runtime\node\24.19.0\node.exe
npm C:\Users\yshs\.vite-plus\js_runtime\node\24.19.0\npm.cmd
npx C:\Users\yshs\.vite-plus\js_runtime\node\24.19.0\npx.cmd

Package Manager:
Name pnpm
Version 11.20.0
Source devEngines.packageManager
Source Path D:\code\Webstorm\vue-demo\package.json
Project Root D:\code\Webstorm\vue-demo
Bin Path C:\Users\yshs\.vite-plus\package_manager\pnpm\11.20.0\pnpm\bin\pnpm.cmd
D:/code/Webstorm/vue-demo
$ vp --version
VITE+ - The Unified Toolchain for the Web

vp v0.2.7

Local vite-plus:
vite-plus v0.2.7

Tools:
vite v8.1.5
rolldown v1.2.0
vitest v4.1.10
oxfmt v0.60.0
oxlint v1.75.0
oxlint-tsgolint v7.0.2001
tsdown v0.22.14

Environment:
Package manager pnpm v11.20.0
Node.js v24.19.0 (.node-version)
```

### Used Package Manager

pnpm

### Logs

```shell

```

### 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).

Reproduce the behavior with the linked vue-demo repository by comparing `pnpm run check` and `vpr check`. Trace how `vpr` supplies package-manager lifecycle variables such as `npm_execpath`, then verify that `npm-run-all2` launches child scripts with pnpm and that the parallel command succeeds without `EBADDEVENGINES`.

Written by the indexing model from the issue text.