docs: 更新 PROJECT-OVERVIEW 规格索引

docs/superpowers/PROJECT-OVERVIEW.md

@@ -268,6 +268,7 @@
 | `docs/superpowers/specs/2026-06-22-食谱推荐系统设计方案.md` | LangGraph Phase 1 | 2026-07-20 |
 | `docs/superpowers/plans/2026-06-24-P1营养师功能实现计划.md` | LangGraph Phase 3 | 2026-07-20 |
 | `docs/superpowers/specs/2026-06-24-P1营养师功能设计方案.md` | LangGraph Phase 3 | 2026-07-20 |
+| `docs/superpowers/specs/2026-08-29-membership-pay-switch-design.md` | 会员费支付开关（payType 分流） | 2026-08-29 |
 
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