Support Vite Task GitHub Actions cache in setup-vp

## Problem

The GitHub Actions cache guide currently asks users to wire Vite Task cache manually with `actions/cache` restore and save steps.

That makes every project choose its own cache path and key shape for `node_modules/.vite/task-cache`. It is easy to get wrong, and users have to repeat the same workflow config in each repository.

## Possible direction

Add first-class Vite Task cache support to `voidzero-dev/setup-vp`.

`setup-vp` could provide a good default path and cache key for Vite Task, while still allowing projects to opt in and override defaults when needed. This should stay separate from package-manager dependency caching.

## Context

Raised during review of #1992. The docs can keep the manual workflow for now, but setup support would make the common case simpler.