fix(pitch-deck): Stale-Closure-Bug im Waiting-Indicator behoben

isWaiting im async Closure war immer true — lokale Variable
firstChunk ersetzt den State-Check zuverlaessig.

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

pitch-deck/components/ui/ChatInterface.tsx

@@ -48,16 +48,16 @@ export default function ChatInterface({ lang }: ChatInterfaceProps) {
       const reader = res.body!.getReader()
       const decoder = new TextDecoder()
       let content = ''
+      let firstChunk = true
 
       while (true) {
         const { done, value } = await reader.read()
         if (done) break
 
-        const chunk = decoder.decode(value, { stream: true })
-        content += chunk
+        content += decoder.decode(value, { stream: true })
 
-        if (isWaiting || content.length === chunk.length) {
-          // First chunk arrived — replace waiting indicator with real content
+        if (firstChunk) {
+          firstChunk = false
           setIsWaiting(false)
           setMessages(prev => [...prev, { role: 'assistant', content }])
         } else {