feat(abacus-react): export new utilities, hooks, and themes

Update index.ts to export:
- ABACUS_THEMES and AbacusThemeName
- Utility functions (numberToAbacusState, calculateBeadDiff, etc.)
- React hooks (useAbacusDiff, useAbacusState)
- New types (BeadState, AbacusState, BeadDiffResult, etc.)

All new features are now available to consumers of the package.

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

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

packages/abacus-react/src/index.ts

@@ -1,5 +1,20 @@
 export { default as AbacusReact } from "./AbacusReact";
-export type { AbacusConfig, BeadConfig, AbacusDimensions } from "./AbacusReact";
+export type {
+  AbacusConfig,
+  BeadConfig,
+  AbacusDimensions,
+  AbacusCustomStyles,
+  BeadStyle,
+  ColumnPostStyle,
+  ReckoningBarStyle,
+  NumeralStyle,
+  ValidPlaceValues,
+  BeadHighlight,
+  StepBeadHighlight,
+  BeadClickEvent,
+  AbacusCallbacks,
+  AbacusOverlay,
+} from "./AbacusReact";
 
 export {
   useAbacusConfig,
@@ -17,3 +32,25 @@ export type {
 
 export { StandaloneBead } from "./StandaloneBead";
 export type { StandaloneBeadProps } from "./StandaloneBead";
+
+export { ABACUS_THEMES } from "./AbacusThemes";
+export type { AbacusThemeName } from "./AbacusThemes";
+
+export {
+  numberToAbacusState,
+  abacusStateToNumber,
+  calculateBeadChanges,
+  calculateBeadDiff,
+  calculateBeadDiffFromValues,
+  validateAbacusValue,
+  areStatesEqual,
+} from "./AbacusUtils";
+export type {
+  BeadState,
+  AbacusState,
+  BeadDiffResult,
+  BeadDiffOutput,
+  PlaceValueBasedBead,
+} from "./AbacusUtils";
+
+export { useAbacusDiff, useAbacusState } from "./AbacusHooks";