feat: add comprehensive zero-config validation system

- Implement self-configuring validation that adapts to system resources
- Add validation for all CRUD operations (add, update, delete, find, relate)
- Auto-configure limits based on available memory (1GB = 10K limit, 8GB = 80K)
- Monitor and auto-tune performance based on query response times
- Fix multiple type filtering with proper anyOf structure
- Enhance type safety by requiring NounType/VerbType enums
- Fix tests to validate correct behavior (no fake implementations)
- Add comprehensive VALIDATION.md documentation
- Update API_REFERENCE.md with validation rules and examples
- Clarify metadata update behavior (null keeps existing, {} clears)

BREAKING CHANGE: getFieldsForType() now requires NounType enum instead of string

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

src/utils/metadataIndex.ts

@@ -8,6 +8,7 @@ import { StorageAdapter } from '../coreTypes.js'
 import { MetadataIndexCache, MetadataIndexCacheConfig } from './metadataIndexCache.js'
 import { prodLog } from './logger.js'
 import { getGlobalCache, UnifiedCache } from './unifiedCache.js'
+import { NounType } from '../types/graphTypes.js'
 
 export interface MetadataIndexEntry {
   field: string
@@ -1959,7 +1960,7 @@ export class MetadataIndexManager {
    * Get fields that commonly appear with a specific entity type
    * Returns fields with their affinity scores (0-1)
    */
-  async getFieldsForType(nounType: string): Promise<Array<{
+  async getFieldsForType(nounType: NounType): Promise<Array<{
     field: string
     affinity: number
     occurrences: number