v1.12.2: live tok/s + ctx display next to status indicator

ChatThroughput renders inline beside StatusDot while streaming or
tool_running. Subscribes to existing usage frames via sessionEvents.
Hides when status drops to idle/error or data is older than 10s.

Addresses the 2026-05-21 spike's UX gap where slow streams looked
identical to dead streams — now there's a live token velocity readout
that immediately distinguishes the two.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/components/ChatTabBar.tsx

@@ -2,6 +2,7 @@ import { useState } from 'react';
 import { Bot, History, MessageSquare, Plus, Terminal, X } from 'lucide-react';
 import type { Chat, WorkspacePane } from '@/api/types';
 import { StatusDot } from '@/components/StatusDot';
+import { ChatThroughput } from '@/components/ChatThroughput';
 import {
   ContextMenu,
   ContextMenuContent,
@@ -99,6 +100,7 @@ export function ChatTabBar({
               >
                 <MessageSquare size={12} className="shrink-0" />
                 <StatusDot chatId={chat.id} />
+                <ChatThroughput chatId={chat.id} />
                 {renamingId === chat.id ? (
                   <input
                     autoFocus