feat(chat): add token & cost estimator badges (M9.6)

Per-message token count badge (e.g. "125 tok", "1.2k tok") next to
timestamp. ContextBar tooltip shows running total and estimated cost
based on model pricing table. Pricing for Claude Haiku/Sonnet/Opus.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/components/chat/ChatMessage.vue

@@ -205,6 +205,8 @@
       <div v-if="!isEditing" class="flex items-center gap-2 mt-1.5">
         <span class="text-[10px] select-none text-white/30">{{ formattedTime }}</span>
         <span v-if="message.editedAt" class="text-[10px] text-white/25 select-none">(edited)</span>
+        <span v-if="showTokenCount" class="text-[10px] text-white/20 select-none" :title="`~${estimatedTokens} tokens`">{{ tokenLabel }}</span>
+        <span v-if="message.feedback" class="text-[10px] select-none">{{ message.feedback === 'up' ? '👍' : '👎' }}</span>
         <button
           v-if="inlineFilms.length > 1"
           class="text-[10px] text-accent/70 hover:text-accent transition-colors"
@@ -457,6 +459,15 @@ const formattedTime = computed(() => {
   return d.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })
 })
 
+// Token estimate (~4 chars per token)
+const estimatedTokens = computed(() => Math.ceil(props.message.content.length / 4))
+const showTokenCount = computed(() => props.message.content.length > 20)
+const tokenLabel = computed(() => {
+  const t = estimatedTokens.value
+  if (t >= 1000) return `${(t / 1000).toFixed(1)}k tok`
+  return `${t} tok`
+})
+
 function openPanelWithContext() {
   updatePanelFromText(props.message.content, props.triggeringQuery, props.message.webResults ?? [])
 }

packages/app/src/components/chat/ChatWindow.vue

@@ -18,7 +18,7 @@
       @scroll-to-message="scrollToMessageIndex"
     />
 
-    <ContextBar :messages="messages" />
+    <ContextBar :messages="messages" :active-model="activeModel" />
 
     <PersonaSelector />
     <MemoryPanel />
@@ -144,7 +144,7 @@ defineEmits<{
 }>()
 
 const chatStore = useChatStore()
-const { sendMessage, stopGeneration, editAndResend, regenerateLastResponse } = useAI()
+const { sendMessage, stopGeneration, editAndResend, regenerateLastResponse, activeModel } = useAI()
 const { updatePanelFromText, panelOpen, activeTab, availableTabs, setActiveTab } = useContentPanel()
 import { useCodeContext } from '@/composables/useCodeContext'
 const codeContext = useCodeContext()

packages/app/src/components/chat/ContextBar.vue

@@ -25,6 +25,7 @@ import type { Message } from '@aiui/core/types/message'
 const props = defineProps<{
   messages: Message[]
   contextWindow?: number
+  activeModel?: string
 }>()
 
 // Default context window sizes per model (tokens)
@@ -44,9 +45,30 @@ const percentage = computed(() => {
   return (estimatedTokens.value / maxTokens.value) * 100
 })
 
+// Model pricing per million tokens (input/output)
+const MODEL_PRICING: Record<string, { input: number; output: number }> = {
+  'claude-haiku-4.5': { input: 0.80, output: 4.00 },
+  'claude-sonnet-4': { input: 3.00, output: 15.00 },
+  'claude-opus-4': { input: 15.00, output: 75.00 },
+}
+
+const estimatedCost = computed(() => {
+  const pricing = MODEL_PRICING[props.activeModel ?? '']
+  if (!pricing) return null
+  // Rough split: 70% input, 30% output
+  const inputTokens = estimatedTokens.value * 0.7
+  const outputTokens = estimatedTokens.value * 0.3
+  const cost = (inputTokens * pricing.input + outputTokens * pricing.output) / 1_000_000
+  return cost
+})
+
 const tooltipText = computed(() => {
   const est = estimatedTokens.value.toLocaleString()
   const max = maxTokens.value.toLocaleString()
-  return `~${est} / ${max} tokens used`
+  let text = `~${est} / ${max} tokens used`
+  if (estimatedCost.value !== null) {
+    text += ` · ~$${estimatedCost.value.toFixed(4)}`
+  }
+  return text
 })
 </script>