Fix duplicate tabs on drag-and-drop and long URL overflow

Guard against Windows/WebView2 firing duplicate drop events by
tracking in-progress paths with a Set ref. Add overflow-wrap and
word-break to markdown content so long unbroken strings wrap.

src/App.tsx

@@ -599,6 +599,7 @@ function App() {
   }, [updateTabScrollState]);
 
   // Tauri native drag-and-drop (bypasses browser event interception)
+  const pendingDropPaths = useRef<Set<string>>(new Set());
   useEffect(() => {
     let unlisten: (() => void) | undefined;
     getCurrentWebview().onDragDropEvent(async (event) => {
@@ -611,6 +612,9 @@ function App() {
         const paths = event.payload.paths;
         const mdPath = paths.find((p: string) => p.endsWith('.md') || p.endsWith('.markdown') || p.endsWith('.txt'));
         if (mdPath) {
+          // Guard against duplicate drop events (Windows/WebView2 fires twice)
+          if (pendingDropPaths.current.has(mdPath)) return;
+          pendingDropPaths.current.add(mdPath);
           try {
             const existing = tabsRef.current.find(t => t.path === mdPath);
             if (existing) {
@@ -628,6 +632,8 @@ function App() {
             }
           } catch (err) {
             console.error('Failed to read dropped file:', err);
+          } finally {
+            pendingDropPaths.current.delete(mdPath);
           }
         }
       }

src/styles.css

@@ -1173,6 +1173,8 @@ html, body, #root {
   max-width: 680px;
   margin: 0 auto;
   color: var(--color-text-primary);
+  overflow-wrap: break-word;
+  word-break: break-word;
 
   /* Premium typography settings */
   font-size: 17px;