fix: make setup script cross-platform (fix #7182)

[scrollDynasty]

Summary

This PR makes the repository setup script cross-platform.

Previously, pnpm run setup used the Unix-specific command rm -rf to remove node_modules, which fails on Windows (PowerShell/CMD) and prevents Windows contributors from completing the setup flow.

Changes

• Replaced rm -rf node_modules with a dependency-free Node.js cleanup script using built-in fs and path.
• Updated the root setup script to use the cleanup script before pnpm install.
• Kept the existing setup flow unchanged:
  • clean node_modules
  • install dependencies
  • prebundle
  • build
• Did not introduce new dependencies or modify pnpm-lock.yaml.

Why not rimraf?

rimraf was considered since it is already used elsewhere in the repository. However, the setup script may run before pnpm install, meaning node_modules binaries (including rimraf) may not exist in fresh clones.

A small Node.js script avoids this bootstrap problem and works in all environments without prerequisites.

Verification

Tested on Windows PowerShell:

node scripts/clean-node-modules.js

Result::

• Exit code: 0
• Works even when node_modules is missing
• Full pnpm run setup was not executed due to its side effects (install, prebundle, build), but the cleanup step integrates without affecting the existing flow.

Related:

• Fixes: pnpm run setup fails on Windows PowerShell/CMD because setup uses rm -rf #7184