fix(compatibility): update status to reflect complete feature parity with Node.js SQLite module

(BackupSync was a hallucination!)

Author: mceachen

COMPATIBILITY.md

@@ -64,25 +64,9 @@ This document tracks our implementation status against Node.js's original `node_
 - ⚠️ **Memory Tracking**: Simplified approach vs Node.js internal tracking
 - ⚠️ **Cleanup Patterns**: Different but equivalent cleanup logic
 
-### ❌ **Missing Features**
+### ✅ **No Missing Features**
 
-#### BackupSync Class
-
-The only significant missing feature is the synchronous backup class:
-
-```typescript
-// Missing synchronous backup class:
-class BackupSync {
-  constructor(sourceDb: DatabaseSync, destinationDb: DatabaseSync,
-              sourceDbName?: string, destinationDbName?: string);
-  step(pages?: number): boolean;
-  close(): void;
-  readonly remainingPages: number;
-  readonly totalPages: number;
-}
-```
-
-However, we provide an async `backup()` method with full functionality including progress callbacks.
+Our implementation is feature-complete with Node.js's SQLite module. All documented APIs are implemented, including the async `backup()` method with full functionality and progress callbacks.
 
 ## Detailed API Comparison
 
@@ -205,19 +189,19 @@ export { DatabaseSync, StatementSync, Session, constants };
 
 ### Upstream Synchronization
 
-- ✅ **SQLite amalgamation** - Synced to version 3.48.0
+- ✅ **SQLite amalgamation** - Synced to version 3.50.0
 - ✅ **Node.js source sync** - Automated sync scripts
 - ✅ **Version tracking** - Automatic version updates in package.json
 
 ## Summary
 
-**Current Implementation Status: ~99% Complete**
+**Current Implementation Status: 100% Complete**
 
-Our implementation provides near-complete compatibility with Node.js's SQLite module. The only missing feature is the synchronous `BackupSync` class, but we provide equivalent functionality through the async `backup()` method.
+Our implementation provides complete compatibility with Node.js's SQLite module. All documented APIs are fully implemented.
 
 **Key Achievements:**
 - All core and advanced SQLite features implemented
-- Full API compatibility with Node.js (except BackupSync)
+- Full API compatibility with Node.js
 - Enhanced with `setReturnArrays()` method not in Node.js
 - Comprehensive test coverage (295 tests passing)
 - Multi-platform support with prebuilds