Build fails when project root is accessed through an NTFS junction

### Describe the bug

When the Vite project root is reached through an NTFS junction (directory symlink), `vp build` fails with:

```
[plugin vite:build-html]
error: The "fileName" or "name" properties of emitted chunks and assets must be strings
that are neither absolute nor relative paths, received
"../../../../../../../actual/real/path/to/frontend/index.html"
```

The `vite:build-html` plugin computes the emitted filename for `index.html` as a relative path from the output directory to the input file. When the project is accessed through a junction, the output directory resolves to the **real path** while the input `index.html` stays on the **junction path**. Since these appear to be on different directory trees, the relative path traverses up to the drive root and back down, producing a `../../../..` path that rolldown rejects.

### Reproduction

1. Create a directory junction on Windows:
```powershell
# Real project lives at D:\Projects\my-app\frontend
cmd /c mklink /J D:\Shortcut\Projects D:\Projects
```

2. Run the build from the junction path:
```bash
cd D:\Shortcut\Projects\my-app\frontend
vp build
```

3. The build fails with the error above. Running the same build from the real path (`D:\Projects\my-app\frontend`) succeeds.

### Root cause

Inside the `vite:build-html` plugin's `generateBundle` hook, the emitted filename for `index.html` is computed as a relative path. One side of the calculation uses the resolved/real path and the other uses the junction path. The mismatch produces an invalid relative path.

### Expected behavior

`vp build` should succeed regardless of whether the working directory is reached through a junction or directly. Paths should be consistently resolved (or consistently left unresolved) before computing relative filenames.

### System Info

```
vp v0.1.16
vite v8.0.5
rolldown v1.0.0-rc.13
Node.js v22.22.1
Windows Server 2025 (win32 x64)
pnpm v10.33.0
```

### Used Package Manager

pnpm

### 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).

Start at the vite:build-html plugin's generateBundle hook, where the emitted filename for index.html is calculated, and reproduce the failure with vp build from an NTFS junction on Windows. Trace how the output directory and input path are resolved; done means the build succeeds from both the junction path and the real project path without producing an absolute or relative emitted filename.

Written by the indexing model from the issue text.