Add TypeScript preference for web stack

Web 项目默认 TypeScript 可减少运行时类型错误并与既有 Node/前端工程保持一致；
对接既有 JS 项目时仍尊重项目自身的语言选择。

CLAUDE.md

@@ -17,6 +17,7 @@ Behavioral guidelines to reduce common LLM coding mistakes. Merge with project-s
   - ❌ Require explicit command every time: delete repo, force-push to `main`/`master`, rewrite published history, change org permissions
   - Prefer a scoped API token over username/password when one becomes available
 - **Package managers**: `pnpm` (Node), `uv` (Python), `cargo` (Rust)
+- **Web stack**: prefer TypeScript over JavaScript (frontend frameworks, Node backends, scripts); follow the existing project's language choice
 - **Indentation**: 4 spaces by default; follow project convention if different
 
 ## 1. Think Before Coding