feat: Add browser extension plugin implementation

[Vorest0628]

📋 修改背景

实现 PowerMem 浏览器扩展插件，为用户提供便捷的网页记忆捕获和管理功能。

✨ 功能特性

• ✅ Chrome Extension Manifest V3 完整实现
• ✅ Popup UI：记忆列表展示与搜索功能
• ✅ Options Page：扩展设置管理
• ✅ Sidebar：最近和相关记忆展示
• ✅ Background Service Worker：右键菜单和快捷键命令
• ✅ Content Script：页面上下文捕获和文本选择
• ✅ 多 Agent/上下文支持
• ✅ 完整的服务层（API 客户端、记忆、存储、通知、推荐）
• ✅ Zustand 状态管理（memory、settings、agent stores）
• ✅ TypeScript 类型定义
• ✅ Vitest 单元测试和 Playwright E2E 测试框架

📦 影响范围

• 新增文件：202 个文件，约 32,397 行代码
• 新增目录：examples/browser-plugin/
• 修改文件：.gitignore（新增 node_modules 排除规则）
• 依赖项：React 18.2+, TypeScript 5.3+, Vite 5.1+, Zustand, Tailwind CSS

🧪 测试验证

• 单元测试：npm run test
• E2E 测试：npm run test:e2e
• 手动测试：参考 docs/WEEK*_TEST_GUIDE.md
• 构建验证：npm run build

📚 文档

• README.md：项目介绍和快速开始
• docs/：周进度总结和测试指南
• 各组件内联 TypeScript 类型定义

🔗 相关链接

• 设计文档：Browser Extension Development Plan
• 实施文档：参见 docs/implementation/week*.md

⚠️ 注意事项

• 需要 Chrome 114+ 或 Edge 114+ 浏览器
• 需要运行 PowerMem API 服务器（默认 http://localhost:8080）
• 首次使用需在 Options 页面配置 API 端点

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📋 Modify background

Implement the PowerMem browser extension to provide users with convenient web page memory capture and management functions.

✨ Features

• ✅ Chrome Extension Manifest V3 fully implemented
• ✅ Popup UI: memory list display and search function
• ✅ Options Page: Extended settings management
• ✅ Sidebar: display of recent and related memories
• ✅ Background Service Worker: right-click menu and shortcut key commands
• ✅ Content Script: page context capture and text selection
• ✅Multi-Agent/context support
• ✅ Complete service layer (API client, memory, storage, notifications, recommendations)
• ✅ Zustand status management (memory, settings, agent stores)
• ✅ TypeScript type definitions
• ✅ Vitest unit testing and Playwright E2E testing framework

📦 Scope of influence

• New files: 202 files, about 32,397 lines of code
• New directory: examples/browser-plugin/
• Modify file: .gitignore (new node_modules exclusion rule)
• Dependencies: React 18.2+, TypeScript 5.3+, Vite 5.1+, Zustand, Tailwind CSS

🧪 Test verification

• Unit test: npm run test
• E2E test: npm run test:e2e
• Manual testing: refer to docs/WEEK*_TEST_GUIDE.md
• Build verification: npm run build

📚 Documentation

• README.md: Project introduction and quick start
• docs/: Weekly progress summary and testing guide
• Inline TypeScript type definitions for each component

🔗 Related links

• Design document: Browser Extension Development Plan
• Implementation documentation: see docs/implementation/week*.md

⚠️ Notes

• Requires Chrome 114+ or Edge 114+ browser
• Requires running PowerMem API server (default http://localhost:8080)
• For first time use, you need to configure the API endpoint on the Options page

[CLAassistant]

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[Teingi]

整体Review意见：

1. 考虑到这个PR量太大了，同时这个PR比较独立。综合考虑之后希望在ob-labs 创建新仓库进行孵化；
2. 代码中有大量的中文注释，期望将其改成英文；

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Overall Review Opinion:

1. Considering that the amount of PR is too large, and at the same time, this PR is relatively independent. After comprehensive consideration, I hope to create a new warehouse in ob-labs for incubation;
2. There are a lot of Chinese comments in the code, and we hope to change them into English;

[Teingi]

https://github.com/ob-labs/powermem-browser-plugin