feat: 标签栏右键菜单 — 关闭其他/右侧/全部标签

新增功能：
- 右键点击标签弹出上下文菜单
- 关闭：关闭当前标签（带未保存确认）
- 关闭其他标签：保留当前，关闭其余（带未保存确认）
- 关闭右侧标签：关闭当前标签右边的所有标签
- 关闭全部标签：关闭所有标签（带未保存确认）
- 点击空白处自动关闭菜单

技术实现：
- tabStore 新增 closeOtherTabs/closeAllTabs/closeTabsToRight 方法
- TabBar 组件新增 ContextMenu 状态管理和右键事件处理
- CSS 新增 .tab-context-menu 样式（暗色主题兼容）

src/renderer/stores/tabStore.ts

@@ -9,6 +9,9 @@ interface TabState {
 
   createTab: (filePath?: string | null, content?: string) => Tab
   closeTab: (tabId: string) => void
+  closeOtherTabs: (tabId: string) => void
+  closeAllTabs: () => void
+  closeTabsToRight: (tabId: string) => void
   switchToTab: (tabId: string) => void
   updateTabContent: (tabId: string, content: string) => void
   setModified: (tabId: string, modified: boolean) => void
@@ -79,6 +82,38 @@ export const useTabStore = create<TabState>((set, get) => ({
     })
   },
 
+  closeOtherTabs: (tabId) => {
+    set(state => {
+      const target = state.tabs.find(t => t.id === tabId)
+      if (!target) return state
+      return {
+        tabs: [target],
+        activeTabId: tabId,
+        mruStack: []
+      }
+    })
+  },
+
+  closeAllTabs: () => {
+    set({ tabs: [], activeTabId: null, mruStack: [] })
+  },
+
+  closeTabsToRight: (tabId) => {
+    set(state => {
+      const index = state.tabs.findIndex(t => t.id === tabId)
+      if (index === -1) return state
+      const newTabs = state.tabs.slice(0, index + 1)
+      const newActiveId = state.activeTabId && newTabs.find(t => t.id === state.activeTabId)
+        ? state.activeTabId
+        : tabId
+      return {
+        tabs: newTabs,
+        activeTabId: newActiveId,
+        mruStack: state.mruStack.filter(id => newTabs.some(t => t.id === id))
+      }
+    })
+  },
+
   switchToTab: (tabId) => {
     set(state => {
       if (state.activeTabId === tabId) return state