feat(abacus-react): add React hooks for abacus calculations

Add AbacusHooks.ts with memoized hooks:
- useAbacusDiff: Calculate bead differences for tutorials
- useAbacusState: Convert numbers to abacus state

These hooks provide performant, memoized access to core utility
functions for use in React components.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/abacus-react/src/AbacusHooks.ts

@@ -0,0 +1,71 @@
+/**
+ * Utility hooks for working with abacus calculations and state
+ */
+
+import { useMemo } from 'react'
+import {
+  calculateBeadDiffFromValues,
+  numberToAbacusState,
+  type BeadDiffOutput,
+  type AbacusState,
+} from './AbacusUtils'
+
+/**
+ * Hook to calculate bead differences between two values
+ * Useful for tutorials, animations, and highlighting which beads need to move
+ *
+ * @param fromValue - Starting value
+ * @param toValue - Target value
+ * @param maxPlaces - Maximum number of place values to consider (default: 5)
+ * @returns BeadDiffOutput with changes, highlights, and summary
+ *
+ * @example
+ * ```tsx
+ * function Tutorial() {
+ *   const diff = useAbacusDiff(5, 15)
+ *
+ *   return (
+ *     <AbacusReact
+ *       value={currentValue}
+ *       stepBeadHighlights={diff.highlights}
+ *     />
+ *   )
+ * }
+ * ```
+ */
+export function useAbacusDiff(
+  fromValue: number | bigint,
+  toValue: number | bigint,
+  maxPlaces: number = 5
+): BeadDiffOutput {
+  return useMemo(() => {
+    return calculateBeadDiffFromValues(fromValue, toValue, maxPlaces)
+  }, [fromValue, toValue, maxPlaces])
+}
+
+/**
+ * Hook to convert a number to abacus state
+ * Memoized for performance when used in components
+ *
+ * @param value - The number to convert
+ * @param maxPlaces - Maximum number of place values (default: 5)
+ * @returns AbacusState representing the bead positions
+ *
+ * @example
+ * ```tsx
+ * function MyComponent() {
+ *   const state = useAbacusState(123)
+ *
+ *   // Check if ones column has heaven bead active
+ *   const onesHasHeaven = state[0].heavenActive
+ * }
+ * ```
+ */
+export function useAbacusState(
+  value: number | bigint,
+  maxPlaces: number = 5
+): AbacusState {
+  return useMemo(() => {
+    return numberToAbacusState(value, maxPlaces)
+  }, [value, maxPlaces])
+}