Whiteboard: Tool-Wechsel bricht Text-Eingabe ab und cleart Cursor-Vorschau

frontend/src/tools/whiteboard.jsx

@@ -838,7 +838,10 @@ export default function Whiteboard({ toast, mobile }) {
           {/* Tools */}
           <div style={{display:'flex',gap:3}}>
             {TOOLS.map(t=>(
-              <button key={t.id} onClick={()=>{setTool(t.id);setSelectedId(null);selectedRef.current=null;}} title={t.tip}
+              <button key={t.id} onClick={()=>{
+                setTool(t.id); setSelectedId(null); selectedRef.current=null;
+                textPreviewRef.current=null; setTextInput(null); render();
+              }} title={t.tip}
                 style={{background:tool===t.id?'rgba(78,205,196,0.2)':'rgba(255,255,255,0.05)',
                   border:`1px solid ${tool===t.id?'#4ECDC4':'rgba(255,255,255,0.1)'}`,
                   borderRadius:7,padding:'5px 9px',color:tool===t.id?'#4ECDC4':'rgba(255,255,255,0.7)',