Workspace Tabs

With tabs enabled the chat surface gains a browser-style strip: conversations, history items and apps live in renamable, persistent tabs.

• Open history in a new tab from the sidebar context menu.
• Each tab owns its own session_id; WebSocket frames are multiplexed with a tabId field and unread badges update per tab.
• State persists locally (gb.tabs.v1) and server-side via GET|PUT /api/user/workspace/tabs.

Tabs stay off by default: activating the picker, opening history into a tab, or ?tabs=1 enables the shell. With a single default tab the payloads are byte-identical to the classic interface.