feat(workspace): add workbench layout and traffic totals

Rework the default /workspace layout into a three-column view
with a left-side Workbench, centered terminal, and right-side
status monitor.

Add a new Workbench pane that groups file manager, command
history, and editor into tabs while preserving panel state.
Extend server status data to expose cumulative network upload
and download totals since boot, and show them in the monitor.

Include a lightweight migration for the old default layout and
update related locale strings, pane metadata, and knowledge
base records.

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

@@ -583,6 +583,9 @@
     "swapLabel": "Swap:",
     "diskLabel": "Disk:",
     "networkLabel": "Network",
+    "totalTrafficLabel": "Traffic Since Boot",
+    "downloadLabel": "Download",
+    "uploadLabel": "Upload",
     "notAvailable": "N/A",
     "bytesPerSecond": "B/s",
     "kiloBytesPerSecond": "KB/s",
@@ -1250,10 +1253,11 @@
     "pane": {
       "connections": "Connections",
       "terminal": "Terminal",
-      "commandBar": "Command Bar",
-      "fileManager": "File Manager",
-      "editor": "Editor",
-      "statusMonitor": "Status Monitor",
+        "commandBar": "Command Bar",
+        "fileManager": "File Manager",
+        "editor": "Editor",
+        "workbench": "Workbench",
+        "statusMonitor": "Status Monitor",
       "commandHistory": "Command History",
       "quickCommands": "Quick Commands",
       "dockerManager": "Docker Manager",
@@ -1262,14 +1266,28 @@
     "panes": {
       "suspendedSshSessions": "Suspended Session Manager"
     },
-    "noActiveSession": {
-      "title": "No Active Session",
-      "message": "Please connect to a session first",
-      "fileManagerSidebar": "File Manager requires an active session",
-      "statusMonitorSidebar": "Status Monitor requires an active session"
-    }
-  },
-  "header": {
+      "noActiveSession": {
+        "title": "No Active Session",
+        "message": "Please connect to a session first",
+        "fileManagerSidebar": "File Manager requires an active session",
+        "statusMonitorSidebar": "Status Monitor requires an active session"
+      }
+    },
+    "workspace": {
+      "noActiveSession": "No active session",
+      "workbench": {
+        "title": "Workbench",
+        "label": "Workspace",
+        "noSession": "No active session",
+        "fileManagerHint": "Activate an SSH session to browse remote files.",
+        "tabs": {
+          "files": "Files",
+          "history": "History",
+          "editor": "Editor"
+        }
+      }
+    },
+    "header": {
     "hide": "Hide",
     "show": "Show Top Navigation"
   },