fix: make package clean scripts work on Windows (#19540)

## Background

Repository builds and tests failed on Windows when four package clean
scripts attempted to execute the unavailable Unix `rm` command.

## Root Cause

The four packages used `rm -rf` instead of the repository's
cross-platform `del-cli`; the reproduction confirmed all scripts exited
127 when `rm` was unavailable.

## Summary

Replaced `rm -rf` with `del-cli` in the test-server, MCP, Hugging Face,
and Baseten package clean scripts.

## Testing

No unit tests were needed for script-only repository tooling; the
recorded cross-platform reproduction and affected package build/test
workflows provide regression coverage.

## End-to-end Validation

- `pnpm -C examples/ai-functions exec tsx
src/reproduction/issue-17951-windows-clean.ts` succeeded with `rm`
unavailable and confirmed all cleanup targets were removed.

## Related Issues

Fixes #17951

Closes #19526

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Co-authored-by: ai-sdk-factory <308175966+ai-sdk-factory@users.noreply.github.com>
Co-authored-by: Gregor Martynus <39992+gr2m@users.noreply.github.com>
Co-authored-by: KushalXCoder <168859142+KushalXCoder@users.noreply.github.com>