feat: implement always-adaptive caching with getCacheStats monitoring

Replaces lazy mode concept with always-adaptive caching strategy:

- Rename getLazyModeStats() → getCacheStats() with enhanced metrics
- Change lazyModeEnabled boolean → cachingStrategy enum ('preloaded' | 'on-demand')
- Update preloading threshold from 30% to 80% for better cache utilization
- Add comprehensive production monitoring and diagnostics
- Add memory detection for containers (Docker/K8s cgroups v1/v2)
- Add adaptive memory sizing from 2GB to 128GB+ systems

Breaking changes: None (backward compatible, deprecated lazy option ignored)

New APIs:
- getCacheStats(): Comprehensive cache performance statistics
- cachingStrategy field: Transparent strategy reporting
- Enhanced fairness metrics and memory pressure monitoring

Documentation:
- Add migration guide for v3.36.0
- Add operations/capacity-planning.md for enterprise deployments
- Update all examples and troubleshooting guides
- Rename monitor-lazy-mode.ts → monitor-cache-performance.ts

src/hnsw/partitionedHNSWIndex.ts

@@ -382,7 +382,7 @@ export class PartitionedHNSWIndex {
   public async removeItem(id: string): Promise<boolean> {
     // Find which partition contains this item
     for (const [partitionId, partition] of this.partitions.entries()) {
-      if (partition.removeItem(id)) {
+      if (await partition.removeItem(id)) {
         // Update metadata
         const metadata = this.partitionMetadata.get(partitionId)!
         metadata.nodeCount = partition.size()