feat: tool timeout auto-retry, file tree attachment, force stop button

- Add configurable tool timeout with auto-retry: when a tool exceeds the
  timeout threshold, abort and send a follow-up message asking Claude to
  try a different approach
- Add "+" button on file tree items to attach files directly to chat
  input via new /api/files/raw endpoint and custom event bridge
- Add force stop button in streaming status bar when tool runs >90s,
  with warning indicators at 60s
- Improve doc preview markdown rendering (padding, list indentation)
- Bump version to 0.10.0

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

src/app/api/chat/route.ts

@@ -10,8 +10,8 @@ export const dynamic = 'force-dynamic';
 
 export async function POST(request: NextRequest) {
   try {
-    const body: SendMessageRequest & { files?: FileAttachment[] } = await request.json();
-    const { session_id, content, model, mode, files } = body;
+    const body: SendMessageRequest & { files?: FileAttachment[]; toolTimeout?: number } = await request.json();
+    const { session_id, content, model, mode, files, toolTimeout } = body;
 
     if (!session_id || !content) {
       return new Response(JSON.stringify({ error: 'session_id and content are required' }), {
@@ -103,6 +103,7 @@ export async function POST(request: NextRequest) {
       abortController,
       permissionMode,
       files: fileAttachments,
+      toolTimeoutSeconds: toolTimeout || 120,
     });
 
     // Tee the stream: one for client, one for collecting the response