feat: comprehensive metadata namespace architecture and cleanup system

BREAKING CHANGE: Remove hard delete option from deleteVerb() for consistent API

- Add complete metadata namespace architecture with O(1) soft delete performance
- Implement periodic cleanup system for old soft-deleted items
- Add restore methods for both nouns and verbs
- Require metadata contracts for all augmentations
- Eliminate namespace collisions with clean separation (_brainy, _augmentations, _audit)
- Optimize index performance using flattened dot-notation for O(1) lookups
- Add comprehensive augmentation safety system with type-safe access control
- Maintain full backward compatibility for existing data
- Add enterprise-grade cleanup with configurable age thresholds and batch processing

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/augmentations/batchProcessingAugmentation.ts

@@ -44,6 +44,7 @@ interface BatchMetrics {
 }
 
 export class BatchProcessingAugmentation extends BaseAugmentation {
+  readonly metadata = 'readonly' as const  // Reads metadata for batching decisions
   name = 'BatchProcessing'
   timing = 'around' as const
   operations = ['add', 'addNoun', 'addVerb', 'saveNoun', 'saveVerb', 'storage'] as ('add' | 'addNoun' | 'addVerb' | 'saveNoun' | 'saveVerb' | 'storage')[]