feat: expose LRU cache hit/miss metrics

[ZacLou]

Summary

Addresses #611

Changes

Added getCacheMetrics() to both FactoryModule and StreamsModule (delegating to the factory):

interface CacheMetrics {
  hits: number;      // total cache hits (positive + negative)
  misses: number;    // total cache misses (contract calls made)
  size: number;      // current entries in the address cache
  hitRate: number;   // hits / (hits + misses), 0 if no requests
}

FactoryModule

• Added _cacheHits and _cacheMisses private counters
• Increment on every cache hit (positive hit returns cached address, negative hit returns null within TTL)
• Increment _cacheMisses on every cache miss (falls through to contract call)
• getCacheMetrics() returns { hits, misses, size, hitRate }
• Counters reset in clearAddressCache()

StreamsModule

• Added getCacheMetrics() proxy delegating to this._factory.getCacheMetrics()

Usage

const sdk = new ConduitClient(config);
const metrics = sdk.streams.getCacheMetrics();
console.log(`Hit rate: ${(metrics.hitRate * 100).toFixed(1)}%`);

Files changed

• src/factory.ts - counters + getCacheMetrics()
• src/streams.ts - getCacheMetrics() proxy