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/adr/0006-monorepo-vue-h5.md

@@ -0,0 +1,21 @@
+# ADR-0006 Monorepo + Vue3 user-h5
+
+## Status
+
+Accepted
+
+## Decision
+
+- npm workspaces Monorepo: `apps/*` + `packages/*`
+- Primary client: Vue 3 + TypeScript + Vite (`apps/user-h5`)
+- Shared network: `packages/sdk`
+
+## Reason
+
+1. Multi-platform path to mini-program via SDK adapters
+2. AI-friendly explicit boundaries
+3. Retire root Legacy HTML gradually
+
+## Never
+
+Never start a second unrelated frontend framework for user-h5 without ADR.