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/walAugmentation.ts

@@ -38,6 +38,7 @@ interface WALConfig {
 export class WALAugmentation extends BaseAugmentation {
   name = 'WAL'
   timing = 'around' as const
+  metadata = 'readonly' as const  // Reads metadata for logging/recovery
   operations = ['addNoun', 'addVerb', 'saveNoun', 'saveVerb', 'updateMetadata', 'delete', 'deleteVerb', 'clear'] as ('addNoun' | 'addVerb' | 'saveNoun' | 'saveVerb' | 'updateMetadata' | 'delete' | 'deleteVerb' | 'clear')[]
   priority = 100 // Critical system operation - highest priority