chore: 添加 Issue 模板、CI 徽章、修复仓库描述

- 新增 bug_report 和 feature_request Issue 模板
- README 添加 GitHub Actions CI 状态徽章
- 修复仓库描述（去重，更新至 v4.2）
- 默认分支改为 main

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -11,6 +11,7 @@
   <img src="https://img.shields.io/badge/typescript-strict-blue" alt="typescript">
   <img src="https://img.shields.io/badge/license-MIT-green" alt="license">
   <img src="https://img.shields.io/badge/tests-72%20passed-brightgreen" alt="tests">
+  <img src="https://github.com/LHY0125/PathEditor/actions/workflows/ci.yml/badge.svg" alt="CI">
 </p>
 
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