chore: seal Design Vision v1 and monorepo scaffold

Archive the differentiated YuXinGu product docs, AI engineering system,
design contract, and Go/Vue scaffold. Next execution prioritizes Cece-parity
over early innovation (see .ai/product/STRATEGY.md).

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

.ai/README.md

@@ -0,0 +1,67 @@
+# AI Engineering System
+
+Machine-readable rules for Cursor / Claude Code / other agents.  
+**Source of truth for engineering constraints.** Prompts are helpers, not the core.
+
+## Priority (what AI depends on most)
+
+1. `constitution.md` — laws
+2. `architecture.md` — layers
+3. `domain.md` — ubiquitous language
+4. `patterns/` — how to implement
+5. `examples/` — copy shapes
+6. `playbooks/` — step flows
+7. `review.md` + `definition-of-done.md` + `checklists/`
+8. `prompts/` — optional task templates
+
+Also always: `ai-contract.md`, `forbidden.md`, `file-map.md`, `workflow.md`, `commands.md`, `adr/`.
+
+## Tree
+
+```
+.ai/
+├── constitution.md
+├── architecture.md
+├── tech-stack.md
+├── domain.md
+├── domain/
+│   └── domain-map.md     # DDD contexts / aggregates
+├── product/
+│   ├── feature-map.md    # 愈心谷 Feature Tree
+│   └── cece-feature-map.md
+├── file-map.md
+├── workflow.md
+├── ai-contract.md
+├── coding.md
+├── api.md
+├── database.md
+├── ui.md                 # IA pointer → design/
+├── design/               # AI Design System Contract
+│   ├── design-system.md
+│   ├── component-catalog.md
+│   └── platform/
+├── deployment.md
+├── testing.md
+├── security.md
+├── review.md
+├── definition-of-done.md
+├── forbidden.md
+├── commands.md
+├── adr/
+├── patterns/
+├── playbooks/
+├── checklists/
+├── examples/
+└── prompts/          # auxiliary
+```
+
+## Cursor
+
+`.cursor/rules|templates|commands` are **symlinks** into this directory.  
+Truth = `.ai/` only. See `../.cursor/README.md`.
+
+## Evolution
+
+See `ROADMAP.md` — Phase 2/3 (anti-patterns, metrics, gates, memory, graph, mcp, skills) are deferred on purpose.
+
+Root entry: `AGENTS.md` · `CLAUDE.md`