feat: implement event subscription and real-time event listener

[Kheshie1]

Summary

Implements event subscription and real-time event listener as described in #33.

/claim #33

Changes

New: src/events.ts — SoroSaveEventListener

• Polls Soroban RPC getEvents endpoint for contract events at configurable interval (default 5s)
• Parses raw events into typed objects: ContributionEvent, PayoutEvent, GroupCreatedEvent, MemberJoinedEvent
• onEvent(eventType, callback) — subscribe to specific event types or '*' for all
• unsubscribe(id) / unsubscribeAll() — cleanup methods
• Cursor persistence via latestCursor / setCursor() so restarts resume without replay
• Re-entrance protection and graceful error handling

Updated: src/types.ts

• Added SoroSaveEventType enum (contribution, payout, group_created, member_joined)
• Added typed event interfaces with - Added typed event interfaces with - Added typed event interfaces with - Added typed event interfaces with src/client.ts
• Added onEvent() convenience method that auto- Added onEvent() convenience method that auto- Added onEvent() convenbscriptions remain
• Added - Added - Added - Added - Addvanced configuration

Updated: src/index.ts

• Exports all new types and the SoroSaveEventListener class

New: t### New: t### New: t### New: t### New: t### New: t### New: `t### New: rsor persistence, event parsing for all 4 types, edge cases (malformed XDR, missing values), and topic name aliasing

Usage

import { SoroSaveClient, SoroSaveEventType } from '@sorosave/sdk';

const client = new SoroSaveClient(config);

// Subscribe to contributions
const subId = client.onEvent(SoroSaveEventType.Contribution, (event) => {
  console.log(`${event.member} contributed ${event.amount} to group ${event.groupId}`);
});

// Later: cleanu// Later: cleanu// Later: cleanu// Later: cleanu// Later: cleanu// Later: cleanu// Later: cleanu// Later: cleanu// Later: cleanu// Later: aveEventType } from '@sorosave/sdk';

const listener = new SoroSaveEventListener({
  rpcUrl: 'https://soroban-testnet.stellar.org',
  contractId: 'CABC...',
  networkPassphrase: Networks.TESTNET,
  pollIntervalMs: 3000,
});

listener.onEvent('*', (event) => conlistener.onEvent('*', (event) => conlistener.onEventor for restart resilience
const cursor = listener.latestCursor;
// On restart: listener.setCursor(cursor);

Tests

All 24 tests pass (21 new + 3 existing):

✓ tests/batch.test.ts (2)
✓ tests/events.test.ts (21)
✓ tests/in✓ tests/in✓ tests/in✓ tests/uthored-By: Oz <oz-agent@warp.dev>