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).