Add comprehensive skills and documentation for various technologies

.claude/skills/frameworks/react/SKILL.md

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+# React
+
+## Description
+
+React component patterns, hooks, and state management best practices.
+
+## When to Use
+
+- Building React components
+- Using React hooks
+- Component state management
+
+---
+
+## Core Patterns
+
+### Functional Components
+
+```tsx
+interface UserCardProps {
+  user: User;
+  onSelect?: (user: User) => void;
+}
+
+export function UserCard({ user, onSelect }: UserCardProps) {
+  return (
+    <div className="card" onClick={() => onSelect?.(user)}>
+      <h3>{user.name}</h3>
+      <p>{user.email}</p>
+    </div>
+  );
+}
+```
+
+### Hooks
+
+```tsx
+// useState
+const [count, setCount] = useState(0);
+
+// useEffect
+useEffect(() => {
+  const subscription = subscribe();
+  return () => subscription.unsubscribe();
+}, [dependency]);
+
+// useMemo
+const expensive = useMemo(() => compute(data), [data]);
+
+// useCallback
+const handleClick = useCallback(() => {
+  doSomething(id);
+}, [id]);
+```
+
+### Custom Hooks
+
+```tsx
+function useUser(id: string) {
+  const [user, setUser] = useState<User | null>(null);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    setLoading(true);
+    fetchUser(id)
+      .then(setUser)
+      .finally(() => setLoading(false));
+  }, [id]);
+
+  return { user, loading };
+}
+```
+
+### Context Pattern
+
+```tsx
+const UserContext = createContext<User | null>(null);
+
+export function UserProvider({ children }: { children: ReactNode }) {
+  const [user, setUser] = useState<User | null>(null);
+
+  return (
+    <UserContext.Provider value={user}>
+      {children}
+    </UserContext.Provider>
+  );
+}
+
+export function useUser() {
+  const context = useContext(UserContext);
+  if (!context) throw new Error('useUser must be within UserProvider');
+  return context;
+}
+```
+
+## Best Practices
+
+1. Keep components small and focused
+2. Use TypeScript for props
+3. Memoize expensive computations
+4. Clean up effects properly
+5. Lift state up when needed
+
+## Common Pitfalls
+
+- **Missing dependencies in hooks**: Include all dependencies
+- **State updates on unmounted**: Use cleanup functions
+- **Prop drilling**: Use context or composition