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/brainyAugmentation.ts

@@ -12,6 +12,15 @@
  * - StreamingPipeline: Enables unlimited data processing
  */
 
+/**
+ * Metadata access declaration for augmentations
+ */
+export interface MetadataAccess {
+  reads?: string[] | '*'      // Fields to read, or '*' for all
+  writes?: string[] | '*'     // Fields to write, or '*' for all  
+  namespace?: string           // Optional: custom namespace like '_myAug'
+}
+
 export interface BrainyAugmentation {
   /**
    * Unique identifier for the augmentation
@@ -27,6 +36,14 @@ export interface BrainyAugmentation {
    */
   timing: 'before' | 'after' | 'around' | 'replace'
   
+  /**
+   * Metadata access contract - REQUIRED
+   * - 'none': No metadata access at all
+   * - 'readonly': Can read any metadata but cannot write
+   * - MetadataAccess: Specific fields to read/write
+   */
+  metadata: 'none' | 'readonly' | MetadataAccess
+  
   /**
    * Which operations this augmentation applies to
    * Granular operation matching for precise augmentation targeting
@@ -125,6 +142,7 @@ export interface AugmentationContext {
 export abstract class BaseAugmentation implements BrainyAugmentation {
   abstract name: string
   abstract timing: 'before' | 'after' | 'around' | 'replace'
+  abstract metadata: 'none' | 'readonly' | MetadataAccess
   abstract operations: (
     // Data Operations
     | 'add' | 'addNoun' | 'addVerb'