docs: mark plan contract completion design as implemented

Implementation of the independent completion page, APIs, badge, and menu is in place pending local SQL apply and UI验收.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/superpowers/specs/2026-08-20-pl-plan-contract-complete-design.md

@@ -2,7 +2,7 @@
 
 > Demo：`docs/fresh-mint-pl-plan-contract-complete-demo.html`（方案 B 为采纳交互）  
 > 日期：2026-08-20  
-> 状态：待实现
+> 状态：已实现（待联调验收）
 
 ## 1. 背景与目标