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 ?? [])
 }