feat(file-tree): comprehensive file tree UI and icon system overhaul

[wuuu1023]

• Add file-type-aware icons for 20+ file formats (TS, JS, Docker, Claude.md, package.json, Markdown, Shell, SQL, YAML, config, etc.)
• Add compact git status prefix indicators (M/D/U/R/!) instead of coloring entire rows
• Add file tree search/filter bar with path matching and auto-expand
• Replace monospace font with system UI font for better readability
• Reduce row height to h-6 for more compact layout
• Switch selection style from bg-muted to bg-accent/80
• Replace CommitFile* components with unified FileTreeFile in git-changes-tab
• Restructure context menus with logical sub-menu grouping
• Remove redundant root folder wrapper, flatten tree display
• Add prefix/suffix/nameClassName/showIcon props to FileTreeFile/Folder
• Tweak indentation and spacing for tighter visual density
• Add unit tests for compact git markers and filter behavior
• Add i18n strings for filter placeholder and no-results message

Chinese (完整版)

feat(file-tree): 文件树 UI 和文件图标系统全面优化

• 新增 20+ 文件类型的智能识别图标（TS、JS、Docker、Claude.md、 package.json、Markdown、Shell、SQL、YAML、配置文件等）
• 使用紧凑的 git 状态前缀标记（M/D/U/R/!）替代整行着色
• 新增文件树搜索/过滤栏，支持路径匹配和自动展开
• 等宽字体改为系统 UI 字体，提升可读性
• 行高压缩至 h-6，布局更紧凑
• 选中样式从 bg-muted 切换为 bg-accent/80
• git-changes-tab 改用统一的 FileTreeFile 组件
• 右键菜单按逻辑分组重构
• 移除冗余的根目录包装层，树形结构更扁平
• 为 FileTreeFile/Folder 新增 prefix/suffix/nameClassName/showIcon 属性
• 调整缩进和间距，视觉密度更紧凑
• 新增 git 标记和过滤功能的单元测试
• 新增过滤占位符和无结果的 i18n 字符串 ---