docs: freeze YuXinGu lexicon, journey, and P1 engineering sources

Establish product language contract, user journey with dual growth engines,
ERD/OpenAPI/Go boundaries, and H5 routes (/profile, /portrait, /relation,
/membership) before P1 implementation.

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

AGENTS.md

@@ -13,7 +13,7 @@ This file is for AI agents.
 5. `.ai/forbidden.md`
 6. `.ai/file-map.md` + `.ai/workflow.md`
 7. Task rules: `.ai/coding.md` / `api.md` / `database.md` / `ui.md` / `security.md` / …
-8. **Product scope / PRD slicing:** `.ai/product/feature-map.md` (竞品对照: `product/cece-feature-map.md`)
+8. **Product scope:** `.ai/product/lexicon.md` + `feature-map.md` + `user-journey.md` + `page-tree.md`（冻结见 `ENGINEERING-FREEZE.md`）
 9. **Any UI work:** `.ai/design/design-system.md` + `component-catalog.md` + matching `design/platform/*.md` (H5 default)
 10. Matching **ADR** in `.ai/adr/` before changing stack or API style
 11. Prefer **patterns/** + **examples/** + **playbooks/** over inventing structure
@@ -41,4 +41,5 @@ Do not invent Phase 2/3 folders (graph/mcp/skills/anti-patterns/…) unless `ROA
 
 ## Product one-liner
 
-Birthday → Profile (digital personality + constitution) → Companion / Ask retention → Membership & Report unlock → Consult later. Compliant lifestyle wording only.
+档案 → 性格探索/个人画像 → 关系理解 → 问答陪伴 → 会员/深度版 →（后）顾问。  
+语言契约：`.ai/product/lexicon.md`。参考竞品模型，不用竞品品牌词与运势/解码叙事。