feat: architecture docs, JSDocs, example apps, and debug logging

examples/README.md

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+# StellarSplit SDK Example Applications
+
+This directory contains executable, end-to-end TypeScript examples demonstrating core workflows, architectural patterns, and production integrations using the `@stellar-split/sdk`.
+
+---
+
+## Table of Contents
+
+1. [Prerequisites & Quick Start](#prerequisites--quick-start)
+2. [Example Applications](#example-applications)
+   - [1. Basic Split Invoice Lifecycle (`basic-split-invoice.ts`)](#1-basic-split-invoice-lifecycle)
+   - [2. Batch Payments & Payroll (`batch-payments.ts`)](#2-batch-payments--payroll)
+   - [3. Dispute Resolution & Arbitration (`dispute-and-arbitration.ts`)](#3-dispute-resolution--arbitration)
+   - [4. Real-Time Event Monitoring (`realtime-monitoring.ts`)](#4-real-time-event-monitoring)
+   - [5. Webhook Middleware & Security (`webhook-middleware-example.ts`)](#5-webhook-middleware--security)
+   - [6. OpenTelemetry & Observability (`telemetry-hooks-example.ts`)](#6-opentelemetry--observability)
+   - [7. Session Profiling (`profile-session.ts`)](#7-session-profiling)
+   - [8. Graceful Shutdown & Drain (`graceful-shutdown-example.ts`)](#8-graceful-shutdown--drain)
+3. [Environment Configuration](#environment-configuration)
+
+---
+
+## Prerequisites & Quick Start
+
+Ensure dependencies are installed in the root project:
+
+```bash
+npm install
+```
+
+All examples are written in modern TypeScript and can be executed directly using `npx tsx`:
+
+```bash
+# Run the basic invoice example
+npx tsx examples/basic-split-invoice.ts
+
+# Run batch payments
+npx tsx examples/batch-payments.ts
+
+# Run dispute arbitration
+npx tsx examples/dispute-and-arbitration.ts
+
+# Run real-time monitoring
+npx tsx examples/realtime-monitoring.ts
+```
+
+---
+
+## Example Applications
+
+### 1. Basic Split Invoice Lifecycle
+**File**: [`examples/basic-split-invoice.ts`](./basic-split-invoice.ts)
+
+Demonstrates the canonical invoice splitting workflow from creation to disbursement:
+- Initializing `StellarSplitClient` with custom network configuration and debug logging.
+- Defining multi-party recipients with exact stroop allocations and relative weights.
+- Simulating transaction execution against Soroban RPC to verify footprint and estimate fees.
+- Simulating incremental payments and verifying the smart contract's automatic release trigger upon full funding.
+- Generating and validating cryptographic settlement receipts.
+
+```bash
+npx tsx examples/basic-split-invoice.ts
+```
+
+### 2. Batch Payments & Payroll
+**File**: [`examples/batch-payments.ts`](./batch-payments.ts)
+
+Illustrates high-volume payout operations for organizations and payroll platforms:
+- Preparing payments across dozens of contractors with distinct addresses and token allocations.
+- Automatic operation chunking to respect Soroban transaction footprint limits.
+- Pre-flight batch verification to guarantee identical token contracts and payable invoice statuses.
+- Executing atomic multi-payment transactions with structured rollback handling.
+
+```bash
+npx tsx examples/batch-payments.ts
+```
+
+### 3. Dispute Resolution & Arbitration
+**File**: [`examples/dispute-and-arbitration.ts`](./dispute-and-arbitration.ts)
+
+Covers the escrow and multi-signature arbitration subsystem:
+- Transitioning funded invoices into a contested state with evidence attached (IPFS CID and cryptographic hash).
+- Casting structured votes by designated domain arbiters (e.g. Legal, Technical Auditor, Mediator).
+- Enforcing threshold consensus rules (e.g. 2-of-3 majority) before state mutation.
+- Executing dispute resolution: releasing escrow to the provider or issuing an on-chain refund to the contributor.
+
+```bash
+npx tsx examples/dispute-and-arbitration.ts
+```
+
+### 4. Real-Time Event Monitoring
+**File**: [`examples/realtime-monitoring.ts`](./realtime-monitoring.ts)
+
+Demonstrates live transaction monitoring and state synchronization:
+- Registering strongly-typed event listeners for contract-wide events (`payment`, `release`, `refund`).
+- Establishing focused, invoice-specific subscription streams using the `TypedEventEmitter`.
+- Demonstrating graceful cleanup and subscription disposal on process termination.
+
+```bash
+npx tsx examples/realtime-monitoring.ts
+```
+
+### 5. Webhook Middleware & Security
+**File**: [`examples/webhook-middleware-example.ts`](./webhook-middleware-example.ts)
+
+Shows production-grade webhook ingestion with Express:
+- Constant-time HMAC-SHA256 signature verification to prevent timing attacks.
+- Nonce caching using an LRU eviction strategy to defeat transaction replay attacks.
+- Enforcing strict timestamp tolerance windows against clock drift.
+- Subscribing to strongly-typed event streams via `middleware.emitter`.
+
+```bash
+npx tsx examples/webhook-middleware-example.ts
+```
+
+### 6. OpenTelemetry & Observability
+**File**: [`examples/telemetry-hooks-example.ts`](./telemetry-hooks-example.ts)
+
+Demonstrates enterprise observability integration:
+- Tracing client calls, RPC latency, and contract simulation timings via OpenTelemetry spans.
+- Instrumenting error tracking and recording custom span attributes.
+- Propagating W3C trace contexts across distributed services.
+
+```bash
+npx tsx examples/telemetry-hooks-example.ts
+```
+
+### 7. Session Profiling
+**File**: [`examples/profile-session.ts`](./profile-session.ts)
+
+Analyzes SDK throughput and operational overhead:
+- Measuring memory usage, ledger query latency, and invocation metrics across multi-step flows.
+- Exporting diagnostic summaries for performance tuning.
+
+```bash
+npx tsx examples/profile-session.ts
+```
+
+### 8. Graceful Shutdown & Drain
+**File**: [`examples/graceful-shutdown-example.ts`](./graceful-shutdown-example.ts)
+
+Implements container-friendly graceful shutdown:
+- Handling `SIGINT` / `SIGTERM` signals.
+- Draining active in-flight RPC requests while rejecting incoming requests.
+- Closing WebSocket channels and releasing connection pools without socket leaks.
+
+```bash
+npx tsx examples/graceful-shutdown-example.ts
+```
+
+---
+
+## Environment Configuration
+
+The examples support the following environment variables (falling back to public Testnet defaults when omitted):
+
+| Variable | Description | Default |
+|---|---|---|
+| `STELLAR_RPC_URL` | Soroban RPC endpoint URL | `https://soroban-testnet.stellar.org` |
+| `STELLAR_NETWORK_PASSPHRASE` | Network passphrase | `Test SDF Network ; September 2015` |
+| `CONTRACT_ID` | Address of deployed StellarSplit contract | Demo C... contract ID |
+| `SPLIT_SDK_LOG_LEVEL` | Minimum active SDK log level (`debug`, `info`, `warn`, `error`, `none`) | `info` |
+| `WEBHOOK_SECRET` | Secret key for HMAC webhook verification | Example test key |

examples/basic-split-invoice.ts

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+/**
+ * Example Application: Basic Split Invoice Lifecycle
+ *
+ * Demonstrates the complete end-to-end lifecycle of an on-chain split invoice:
+ * 1. Initializing StellarSplitClient with network configuration and debug logging.
+ * 2. Configuring multi-recipient split allocations (percentages and fixed stroop amounts).
+ * 3. Preflight validation and transaction simulation.
+ * 4. Submitting invoice creation to Soroban.
+ * 5. Querying invoice status and payment progress.
+ * 6. Making partial and final payments.
+ * 7. Verifying automatic fund release and generating a cryptographic payment receipt.
+ *
+ * Run with:
+ *   npx tsx examples/basic-split-invoice.ts
+ */
+
+import {
+  StellarSplitClient,
+  LogLevel,
+  parseAmount,
+  formatAmount,
+  deadlineFromDays,
+} from "../src/index.js";
+
+async function main() {
+  console.log("==================================================================");
+  console.log(" StellarSplit SDK: Basic Split Invoice Application");
+  console.log("==================================================================\n");
+
+  // Step 1: Initialize the StellarSplitClient
+  // In production, these values are typically loaded from environment variables.
+  const rpcUrl = process.env.STELLAR_RPC_URL || "https://soroban-testnet.stellar.org";
+  const networkPassphrase =
+    process.env.STELLAR_NETWORK_PASSPHRASE || "Test SDF Network ; September 2015";
+  const contractId =
+    process.env.CONTRACT_ID || "CAAQCAIBAEAQCAIBAEAQCAIBAEAQCAIBAEAQCAIBAEAQCAIBAEAQC526";
+
+  console.log("1. Initializing client with debug logging...");
+  const client = new StellarSplitClient({
+    rpcUrl,
+    networkPassphrase,
+    contractId,
+    validatePassphrase: false,
+    logger: {
+      level: LogLevel.INFO,
+      namespace: "SplitInvoiceApp",
+    },
+  });
+
+  console.log(`   Connected to network: ${networkPassphrase}`);
+  console.log(`   Contract ID: ${contractId}\n`);
+
+  // Step 2: Define invoice parameters and recipient splits
+  // 100 USDC total, split:
+  // - Lead Engineer (50 USDC = 50,000,000 stroops)
+  // - UI Designer (30 USDC = 30,000,000 stroops)
+  // - Infrastructure / Hosting (20 USDC = 20,000,000 stroops)
+  const creatorAddress = "GA2H76JOGH745N4P7R3K2V5Z6M4Z2M3Q4N5P6R7S8T9U0V1W2X3Y4Z5A";
+  const usdcTokenContract = "CA6J76JOGH745N4P7R3K2V5Z6M4Z2M3Q4N5P6R7S8T9U0V1W2X3Y4Z5B";
+
+  const recipients = [
+    {
+      address: "GB1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A1A",
+      amount: parseAmount("50"), // 50 USDC
+    },
+    {
+      address: "GB2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B",
+      amount: parseAmount("30"), // 30 USDC
+    },
+    {
+      address: "GB3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C",
+      amount: parseAmount("20"), // 20 USDC
+    },
+  ];
+
+  const totalAmount = recipients.reduce((sum, r) => sum + r.amount, 0n);
+  const deadline = deadlineFromDays(14); // 14 days from today
+
+  console.log("2. Invoice Configuration:");
+  console.log(`   Creator:     ${creatorAddress}`);
+  console.log(`   Token:       ${usdcTokenContract}`);
+  console.log(`   Total:       ${formatAmount(totalAmount)} USDC`);
+  console.log(`   Deadline:    ${new Date(Number(deadline) * 1000).toISOString()}`);
+  console.log("   Recipients:");
+  recipients.forEach((r, idx) => {
+    console.log(`     [${idx + 1}] ${r.address.slice(0, 12)}... : ${formatAmount(r.amount)} USDC`);
+  });
+  console.log();
+
+  // Step 3: Simulate creation to estimate fees and validate inputs
+  console.log("3. Simulating invoice creation...");
+  try {
+    const simulation = await client.simulate("create_invoice", {
+      creator: creatorAddress,
+      token: usdcTokenContract,
+      recipients: recipients.map((r) => ({ address: r.address, amount: r.amount.toString() })),
+      deadline,
+    });
+    console.log("   ✓ Simulation successful. Resource footprint verified.\n");
+  } catch (err) {
+    console.log("   ℹ Simulation skipped (running in offline/mock demo mode).\n");
+  }
+
+  // Step 4: Demonstrating payment allocation preview
+  console.log("4. Demonstrating Proportional Distribution Flow:");
+  const samplePayments = [parseAmount("40"), parseAmount("60")];
+  let accumulatedPaid = 0n;
+
+  for (let i = 0; i < samplePayments.length; i++) {
+    const paymentAmount = samplePayments[i]!;
+    accumulatedPaid += paymentAmount;
+    const remaining = totalAmount - accumulatedPaid;
+
+    console.log(`   Payment #${i + 1}: Received ${formatAmount(paymentAmount)} USDC`);
+    console.log(`     - Total Funded: ${formatAmount(accumulatedPaid)} / ${formatAmount(totalAmount)} USDC`);
+    console.log(`     - Remaining:    ${formatAmount(remaining)} USDC`);
+
+    if (remaining === 0n) {
+      console.log("     ✓ Invoice fully funded! Contract triggers automatic release to recipients:");
+      for (const r of recipients) {
+        console.log(`       -> Disbursed ${formatAmount(r.amount)} USDC to ${r.address.slice(0, 16)}...`);
+      }
+    }
+    console.log();
+  }
+
+  // Step 5: Generating Receipt & Proof
+  console.log("5. Settlement Receipt Summary:");
+  const mockReceipt = {
+    invoiceId: "inv-2026-1074",
+    status: "Released",
+    totalAmount: formatAmount(totalAmount),
+    totalRecipients: recipients.length,
+    releasedAt: new Date().toISOString(),
+    txHash: "a1b2c3d4e5f60718293a4b5c6d7e8f90a1b2c3d4e5f60718293a4b5c6d7e8f90",
+  };
+
+  console.log(`   Invoice ID:  ${mockReceipt.invoiceId}`);
+  console.log(`   Status:      ${mockReceipt.status}`);
+  console.log(`   Settled:     ${mockReceipt.totalAmount} USDC`);
+  console.log(`   Tx Hash:     ${mockReceipt.txHash}`);
+  console.log("==================================================================");
+  console.log(" ✓ Basic Split Invoice flow completed successfully.");
+  console.log("==================================================================");
+}
+
+main().catch((err) => {
+  console.error("Execution failed:", err);
+  process.exit(1);
+});