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/ROADMAP.md

@@ -0,0 +1,38 @@
+# AI System Evolution Roadmap
+
+Do **not** build everything at once. Rules have maintenance cost.
+
+## Phase 1 — Now (shipped)
+
+- Rules: constitution, architecture, domain, coding, api, database, ui, …
+- ADR, patterns, examples, playbooks
+- Review / DoD / checklists / forbidden / commands / workflow / file-map
+- `ai-contract.md`
+- Cursor runtime: `.cursor/*` → symlink → `.ai/` (no content copy)
+
+**Invest next engineering time in:** polishing `patterns/`, `examples/`, `playbooks/` while building real features — not more rule files.
+
+## Phase 2 — When the codebase grows
+
+Add only when pain appears:
+
+| Item | Why wait |
+|---|---|
+| `anti-patterns/` | Useful after real mistakes accumulate |
+| `metrics.md` | Numbers matter once CI exists |
+| `quality-gates.md` | Wire when lint/test gates are real |
+| `memory/` (known-bugs, tech-debt, todo) | Fill from actual incidents |
+
+## Phase 3 — Multi-agent / heavy automation
+
+| Item | Why wait |
+|---|---|
+| `graph/domain.yaml` | Knowledge graph for relation reasoning |
+| `mcp/*.json` | Structured context servers |
+| `skills/<feature>/` | Packaged feature kits (login, payment, …) |
+
+Markdown remains human-readable; JSON/YAML for machines — introduce when agents > 1 or retrieval latency hurts.
+
+## Rule of thumb
+
+If adding a rule file does not prevent a repeated AI failure this week, **do not add it**.