feat(web): integrate Claude LLM streaming with markdown rendering

- Add Anthropic SDK with DeepSeek-compatible API config
- Streaming tool-use loop in WebSocket chat handler
- GitHub-style markdown rendering with markdown-it
- Tool status indicators and thinking states in chat UI
- Fix Tailwind content path and CSS border utility

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/client/src/components/chat/ChatMessage.tsx

@@ -1,18 +1,31 @@
 import { cn } from '@/lib/utils';
+import { renderMarkdown } from '@/lib/markdown';
 import type { Message } from '@/types';
 
 export function ChatMessage({ message }: { message: Message }) {
   const isUser = message.role === 'user';
+  const isEmpty = !message.content;
 
   return (
     <div className={cn('mb-4 flex', isUser ? 'justify-end' : 'justify-start')}>
       <div
         className={cn(
-          'max-w-[80%] rounded-lg px-4 py-2.5 text-sm leading-relaxed',
-          isUser ? 'bg-zinc-800 text-zinc-100' : 'bg-zinc-900 text-zinc-300 border border-zinc-800'
+          'max-w-[80%] rounded-lg px-4 py-2.5',
+          isUser
+            ? 'bg-zinc-800 text-zinc-100'
+            : 'bg-zinc-900 text-zinc-300 border border-zinc-800'
         )}
       >
-        {message.content}
+        {isEmpty ? (
+          <span className="text-zinc-600 italic text-xs">...</span>
+        ) : isUser ? (
+          <p className="text-sm leading-relaxed whitespace-pre-wrap">{message.content}</p>
+        ) : (
+          <div
+            className="markdown-body text-sm leading-relaxed"
+            dangerouslySetInnerHTML={{ __html: renderMarkdown(message.content) }}
+          />
+        )}
       </div>
     </div>
   );