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/entityRegistryAugmentation.ts

@@ -54,6 +54,7 @@ export interface EntityMapping {
  * Optimized for streaming data scenarios like Bluesky firehose processing
  */
 export class EntityRegistryAugmentation extends BaseAugmentation {
+  readonly metadata = 'readonly' as const  // Reads metadata to register entities
   readonly name = 'entity-registry'
   readonly description = 'Fast external-ID to internal-UUID mapping for streaming data'
   readonly timing: 'before' | 'after' | 'around' | 'replace' = 'before'
@@ -469,6 +470,7 @@ export class EntityRegistryAugmentation extends BaseAugmentation {
 
 // Hook into Brainy's add operations to automatically register entities
 export class AutoRegisterEntitiesAugmentation extends BaseAugmentation {
+  readonly metadata = 'readonly' as const  // Reads metadata for auto-registration
   readonly name = 'auto-register-entities'
   readonly description = 'Automatically register entities in the registry when added'
   readonly timing: 'before' | 'after' | 'around' | 'replace' = 'after'