feat: add resource management types and utilities for memory optimization

- Add Disposable, BufferConfig, MemoryMetrics, CleanupRegistration types
- Create src/config/buffer-limits.ts with consolidated buffer size constants
- Create src/config/map-limits.ts with Map size limits to prevent unbounded growth
- Implement BufferAccumulator utility with configurable trim and onTrim callback
- Implement LRUMap with automatic eviction and O(1) operations
- Implement CleanupManager for unified resource cleanup with isStopped guard
- Add comprehensive tests for all new utilities

This lays the foundation for memory leak prevention and performance improvements.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/utils/index.ts

@@ -0,0 +1,11 @@
+/**
+ * @fileoverview Utility module exports.
+ *
+ * This module re-exports all utility classes and functions for easy import.
+ *
+ * @module utils
+ */
+
+export { BufferAccumulator } from './buffer-accumulator.js';
+export { LRUMap, type LRUMapOptions } from './lru-map.js';
+export { CleanupManager, type TimerOptions } from './cleanup-manager.js';