fix: relocate typing indicator into the input bubble

Move TypingIndicator from document flow (between MessageList and
MessageInput) into MessageInput's outer wrapper using absolute
bottom-full positioning. Fixes indicator being hidden behind the
floating glass input bubble on desktop.

packages/web/src/components/chat/TypingIndicator.tsx

@@ -30,7 +30,7 @@ export function TypingIndicator({ channelId }: TypingIndicatorProps) {
   }
 
   return (
-    <div className="h-[24px] px-4 flex items-center text-[12px] text-txt-primary font-medium select-none pointer-events-none">
+    <div className="absolute bottom-full left-1 md:left-4 mb-1 px-3 flex items-center text-[12px] text-txt-secondary font-medium select-none pointer-events-none animate-typing-in motion-reduce:animate-none">
       <div className="flex items-center gap-2">
         <div className="flex gap-[2px] bg-surface-elevated/20 rounded-full px-2 py-1">
           <div className="w-[5px] h-[5px] bg-txt-message rounded-full animate-bounce" style={{ animationDelay: '0ms', animationDuration: '0.8s' }} />