fix: export ImportManager and add getStats() convenience method

Resolves API accessibility issues reported by Brain Cloud Studio team:

1. Export ImportManager and createImportManager
   - ImportManager class was fully implemented but not exported
   - Consumers can now access AI-powered import features
   - Includes ImportOptions and ImportResult types

2. Add brain.getStats() convenience method
   - Documentation showed getStats() as top-level method
   - Implementation had it nested under brain.counts.getStats()
   - Added convenience method that delegates to counts API
   - Maintains backward compatibility

3. Update API documentation
   - Corrected getStats() signature and return type
   - Added comprehensive ImportManager documentation
   - Included examples for all import patterns

These changes expose existing, tested functionality without
modifying core behavior. All tests pass.

src/index.ts

@@ -62,14 +62,18 @@ export {
 
 // Export Neural Import (AI data understanding)
 export { NeuralImport } from './cortex/neuralImport.js'
-export type { 
+export type {
   NeuralAnalysisResult,
   DetectedEntity,
   DetectedRelationship,
   NeuralInsight,
-  NeuralImportOptions 
+  NeuralImportOptions
 } from './cortex/neuralImport.js'
 
+// Export Import Manager (comprehensive data import)
+export { ImportManager, createImportManager } from './importManager.js'
+export type { ImportOptions, ImportResult } from './importManager.js'
+
 // Augmentation types are already exported later in the file
 
 // Export distance functions for convenience