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

docs/guides/getting-started.md

@@ -30,7 +30,7 @@ await brain.init()
 const brain = new Brainy({
   // Storage configuration
   storage: {
-    type: 'filesystem',  // or 's3', 'opfs', 'memory'
+    type: 'filesystem',  // or 's3', 'opfs'
     path: './my-data'
   },
   
@@ -218,12 +218,12 @@ async function processStream(item) {
 
 ## Storage Options
 
-### Development (Memory)
+### Development (FileSystem)
 ```typescript
 const brain = new Brainy({
-  storage: { type: 'memory' }
+  storage: { type: 'filesystem', path: '/tmp/brainy-dev' }
 })
-// Fast, temporary, perfect for testing
+// Fast, persistent, perfect for testing
 ```
 
 ### Production (FileSystem)