feat: expose neural entity extraction APIs (v5.7.6 - Workshop request)

Addresses Workshop team's request for direct access to neural extraction classes.

**Changes:**

1. **New Exports** (src/index.ts):
   - `NeuralEntityExtractor` - Full extraction orchestrator
   - `SmartExtractor` - Entity type classifier (4-signal ensemble)
   - `SmartRelationshipExtractor` - Relationship type classifier
   - Types: `ExtractedEntity`, `ExtractionResult`, `RelationshipExtractionResult`, etc.

2. **Package.json Subpath Exports**:
   ```typescript
   // Enable direct imports:
   import { NeuralEntityExtractor } from '@soulcraft/brainy/neural/entityExtractor'
   import { SmartExtractor } from '@soulcraft/brainy/neural/SmartExtractor'
   import { SmartRelationshipExtractor } from '@soulcraft/brainy/neural/SmartRelationshipExtractor'
   ```

3. **New brain.extractEntities() Method** (brainy.ts:3254):
   - Alias for `brain.extract()` with clearer naming
   - Documented with examples and architecture details
   - 4-signal ensemble: ExactMatch (40%) + Embedding (35%) + Pattern (20%) + Context (5%)

4. **Comprehensive Documentation** (docs/neural-extraction.md):
   - Complete neural extraction guide (200+ lines)
   - API reference for all extraction classes
   - Performance optimization tips
   - Import preview mode documentation
   - Confidence scoring explanation
   - 42 NounType detection methods
   - Troubleshooting guide
   - Real-world examples

5. **README Updates**:
   - Added "Entity Extraction" section with examples
   - Links to neural extraction guide
   - Import preview mode link

**Features:**
- ⚡ Fast extraction: ~15-20ms per entity
- 🎯 4-signal ensemble architecture
- 📊 Format intelligence (Excel, CSV, PDF, YAML, DOCX, JSON, Markdown)
- 🌍 42 universal noun types + 127 verb types
- 💾 LRU caching built-in
- 🧪 Production-tested in import pipeline

**Usage:**

```typescript
// Simple API (recommended)
const entities = await brain.extractEntities('John Smith founded Acme Corp', {
  types: [NounType.Person, NounType.Organization],
  confidence: 0.7
})

// Advanced API (custom configuration)
import { SmartExtractor } from '@soulcraft/brainy'

const extractor = new SmartExtractor(brain, { minConfidence: 0.8 })
const result = await extractor.extract('CEO', {
  formatContext: { format: 'excel', columnHeader: 'Title' }
})
```

**Backward Compatible:** All existing APIs unchanged. New exports are pure additions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/brainy.ts

@@ -3228,6 +3228,41 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     return await this._extractor.extract(text, options)
   }
 
+  /**
+   * Extract entities from text (alias for extract())
+   * v5.7.6: Added for API clarity and Workshop team request
+   *
+   * Uses NeuralEntityExtractor with SmartExtractor ensemble (4-signal architecture):
+   * - ExactMatch (40%) - Dictionary lookups
+   * - Embedding (35%) - Semantic similarity
+   * - Pattern (20%) - Regex patterns
+   * - Context (5%) - Contextual hints
+   *
+   * @param text - Text to extract entities from
+   * @param options - Extraction options
+   * @returns Array of extracted entities with types and confidence scores
+   *
+   * @example
+   * ```typescript
+   * const entities = await brain.extractEntities('John Smith founded Acme Corp', {
+   *   confidence: 0.7,
+   *   types: [NounType.Person, NounType.Organization],
+   *   neuralMatching: true
+   * })
+   * ```
+   */
+  async extractEntities(
+    text: string,
+    options?: {
+      types?: NounType[]
+      confidence?: number
+      includeVectors?: boolean
+      neuralMatching?: boolean
+    }
+  ): Promise<ExtractedEntity[]> {
+    return this.extract(text, options)
+  }
+
   /**
    * Extract concepts from text
    *

src/index.ts

@@ -70,6 +70,23 @@ export type {
   NeuralImportOptions
 } from './cortex/neuralImport.js'
 
+// Export Neural Entity Extraction (v5.7.6 - Workshop request)
+export { NeuralEntityExtractor } from './neural/entityExtractor.js'
+export { SmartExtractor } from './neural/SmartExtractor.js'
+export { SmartRelationshipExtractor } from './neural/SmartRelationshipExtractor.js'
+export type {
+  ExtractedEntity
+} from './neural/entityExtractor.js'
+export type {
+  ExtractionResult,
+  SmartExtractorOptions,
+  FormatContext
+} from './neural/SmartExtractor.js'
+export type {
+  RelationshipExtractionResult,
+  SmartRelationshipExtractorOptions
+} from './neural/SmartRelationshipExtractor.js'
+
 // Import Manager removed - use brain.import() instead (available on all Brainy instances)
 
 // Augmentation types are already exported later in the file