sp-map-joined-chain — removed 2026-10-23 (Asia/Shanghai)

这篇还没有中文，下面是英文原文。

Status: removed. map then joined versus reduce(into:) was about 1.18× (2.023 ms versus 1.717 ms, 200 items × 400 reps, swiftc -O). Checksums matched. No matcher.

• Slug never reused.
• The old blocked note stays beside this file. Fixtures are under _removed/fixtures/.