Summary

Reverts #49. Right after that PR deployed, pnpm started failing to install
@voidzero-dev/vite-plus-core preview builds from this bridge:

ERR_PNPM_TARBALL_EXTRACT  Failed to add tarball from
"https://registry-bridge.viteplus.dev/tarballs/@voidzero-dev/vite-plus-core/0.0.0-commit.14f13284edd3755ac46a3af4632c562d53645368.tgz"
to store: Invalid checksum for TAR header at offset 5038080. Expected 0, got NaN

That points at corrupted/truncated tarball bytes, and #49 rewrote the
byte-assembly logic in fetchUpstreamTarball (the buffer this preview
package's on-demand build path streams the upstream download into before
repacking). Reverting to restore service while the actual defect gets a
proper root-cause fix backed by a reproduction test.

Test plan

• pnpm typecheck
• pnpm test (77/77, back to the pre-Reduce per-request CPU/memory in workspace-package check and tarball fetch #49 baseline)
• Diff against pre-Reduce per-request CPU/memory in workspace-package check and tarball fetch #49 main is empty