fix(repo): make scripts work on Windows

[tosincarik]

What changed

• Make package scripts Windows-compatible by avoiding unix-only rm -rf
• Avoid command chaining by using prebuild/posttest hooks
• Stabilize reranking response snapshots by ignoring content-length

Why

• Windows environments fail to build/test when scripts rely on rm
• Snapshot mismatches can occur due to platform-dependent headers

Notes

• Changes are limited to script/snapshot stability; no runtime behavior changes intended.

[tosincarik]

Vercel check is failing with “Authorization required to deploy” (fork deployment gate).
The Vercel UI says it’s awaiting authorization by a member of the Vercel Labs Team.
Could a maintainer please click “Approve deployment” (or mark the Vercel preview check as non-required) so CI can go green?