feat(frontend): 重构工作区终端与导航交互

将 SSH 顶部标签改为服务器级切换入口，并把同服务器下的
多终端切换、新增与关闭下沉到终端面板内部，修正服务器与
终端的视觉层级

同时将 Workbench 导航改为左侧图标栏，并为终端标签右键菜单
补充“关闭全部”动作，完善相关多语言文案与工作区事件处理

packages/frontend/src/locales/en-US.json

@@ -1628,7 +1628,9 @@
     "showTransferProgressTooltip": "Show/Hide Transfer Progress",
     "newTerminalTooltip": "Open another terminal for the current server",
     "openConnectionPickerTooltip": "Choose another server",
-    "terminalBadge": "Terminal {index}"
+    "terminalBadge": "Terminal {index}",
+    "serverEntryTitle": "{name} · {count} terminals",
+    "terminalCount": "{count} terminals"
   },
   "tabs": {
     "contextMenu": {

packages/frontend/src/locales/ja-JP.json

@@ -1590,6 +1590,19 @@
           "openConnectionPickerTooltip": "別のサーバーを選択",
           "terminalBadge": "端末 {index}"
       },
+      "tabs": {
+        "contextMenu": {
+          "close": "タブを閉じる",
+          "closeAll": "すべて閉じる",
+          "closeOthers": "他のタブを閉じる",
+          "closeRight": "右側のタブを閉じる",
+          "closeLeft": "左側のタブを閉じる",
+          "suspendSession": "セッションを中断",
+          "unmarkForSuspend": "中断マークを解除"
+        },
+        "closeTabTooltip": "タブを閉じる",
+        "newTabTooltip": "新しい接続タブ"
+      },
       "workspace": {
         "terminal": {
             "reconnectingMsg": "再接続を試行中..."

packages/frontend/src/locales/zh-CN.json

@@ -1632,7 +1632,9 @@
     "showTransferProgressTooltip": "显示/隐藏传输进度",
     "newTerminalTooltip": "为当前服务器新增终端",
     "openConnectionPickerTooltip": "选择其他服务器",
-    "terminalBadge": "终端 {index}"
+    "terminalBadge": "终端 {index}",
+    "serverEntryTitle": "{name} · {count} 个终端",
+    "terminalCount": "{count} 个终端"
   },
   "tabs": {
     "contextMenu": {