docs(rfc): restore the checkpoint paragraph break lost in the #4894 merge

[huangruiteng]

Why

The #4894 merge resolved an additive conflict in
docs/architecture/rfcs/typescript-control-plane-migration-v0.md by keeping both
## Current implementation checkpoint paragraphs, newest first. The blank line
between them was staged only for the zh-CN mirror, so on main the English
section renders those two entries as a single paragraph while zh-CN renders
two.

What changed

One blank line, in the English RFC only. No text is added, removed or reordered;
the zh-CN mirror already carries the break.

Validation

• parity check between the two locales after the change: both now separate the
  canonical-lease-renew operator-contract sentence from the handoff-mode
  entry;
• git diff --stat: 1 file, 1 insertion.

Public-docs-only change, so it follows the narrow self-merge allowance: exact-head
review published, merge-readiness checked immediately before merge.

[huangruiteng]

Approval conclusion (author-owned PR; GitHub blocks formal self-approval)

Reviewed exact head 5eb6734107ef355c698992395536f07fee903733.

动机

#4894 合并时在该 RFC 的 ## Current implementation checkpoint 顶部遇到纯追加冲突：main 与本分支各自新增了一段 checkpoint。冲突解决保留了双方文本，最新在前，但两段之间的空行只进了 zh-CN 镜像，英文版因此把两条 checkpoint 渲染成同一个段落，而镜像版渲染成两段。修复的是这个不一致，不是任何 checkpoint 内容。

改动思路

只补回英文版缺失的空行，使两个 locale 的段落结构一致。没有重排、删减或改写任何一句 checkpoint 文本，也没有触碰 Markdown 之外的内容，因此不需要新的 owner 或格式约定。

具体改动

docs/architecture/rfcs/typescript-control-plane-migration-v0.md：在 canonical lease operator contract 句与 handoff-mode checkpoint 段之间插入一个空行。zh-CN 镜像已具备该空行，未改动。

对主干的风险

无行为、契约或发布面风险；纯公开文档格式修复，git diff --stat 为 1 file / 1 insertion。唯一需要留意的相邻风险是同一区域未来再次冲突时仍应两侧保留，这一点已由两篇 RFC 的最终文本本身固定。

我的整体评价

范围最小且原因明确：修复的是我自己在上一次合并解决中留下的单行缺陷（空行只 staged 进 zh-CN），因此按公开文档的自合并通道处理，并在 exact head 上发布本评审。

English verdict: APPROVE at exact head 5eb6734 - a one-line blank-line restoration that makes the English RFC match its zh-CN mirror; docs-only, no behavioral surface.