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/utils/metadataFilter.ts

@@ -95,7 +95,12 @@ function matchesQuery(value: any, query: any): boolean {
       case 'notEquals':
       case 'isNot':
       case 'ne':
+        // Special handling: if value is undefined and operand is not undefined,
+        // they are not equal (so the condition passes)
+        // This ensures items without a 'deleted' field match 'deleted !== true'
         if (value === operand) return false
+        // If value is undefined and operand is not, they're not equal (pass)
+        // If both are undefined, they're equal (fail, handled above)
         break
         
       // Comparison operators