Feat:Can directly generate an agent node by dragging and dropping the connecting line (#9226) (#9357)

…e connecting line (#9226)

### What problem does this PR solve?

Can directly generate an agent node by dragging and dropping the
connecting line (#9226)

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

web/src/pages/agent/canvas/context.tsx

@@ -0,0 +1,56 @@
+import {
+  createContext,
+  ReactNode,
+  useCallback,
+  useContext,
+  useRef,
+} from 'react';
+
+interface DropdownContextType {
+  canShowDropdown: () => boolean;
+  setActiveDropdown: (type: 'handle' | 'drag') => void;
+  clearActiveDropdown: () => void;
+}
+
+const DropdownContext = createContext<DropdownContextType | null>(null);
+
+export const useDropdownManager = () => {
+  const context = useContext(DropdownContext);
+  if (!context) {
+    throw new Error('useDropdownManager must be used within DropdownProvider');
+  }
+  return context;
+};
+
+interface DropdownProviderProps {
+  children: ReactNode;
+}
+
+export const DropdownProvider = ({ children }: DropdownProviderProps) => {
+  const activeDropdownRef = useRef<'handle' | 'drag' | null>(null);
+
+  const canShowDropdown = useCallback(() => {
+    const current = activeDropdownRef.current;
+    return !current;
+  }, []);
+
+  const setActiveDropdown = useCallback((type: 'handle' | 'drag') => {
+    activeDropdownRef.current = type;
+  }, []);
+
+  const clearActiveDropdown = useCallback(() => {
+    activeDropdownRef.current = null;
+  }, []);
+
+  const value: DropdownContextType = {
+    canShowDropdown,
+    setActiveDropdown,
+    clearActiveDropdown,
+  };
+
+  return (
+    <DropdownContext.Provider value={value}>
+      {children}
+    </DropdownContext.Provider>
+  );
+};