Implement unified Discoverer + Enhancer architecture

- Rename AutoEnhancer to Discoverer with clear element discovery focus
- Implement unified enhancement pipeline in Enhancer:
  * Phase 1: Element Discovery (configurable, respects existing insertr classes)
  * Phase 2: ID Generation via engine
  * Phase 3: Content Injection via engine
- Add EnhancementConfig and DiscoveryConfig for flexible configuration
- Update all method names and references (discoverNode, DiscoveryResult, etc.)
- Support both manual class insertion and automatic discovery
- Maintain single enhance command interface while providing unified internal pipeline
- Update all constructors to use new configuration-based approach

This establishes the clean Discoverer + Enhancer architecture discussed, with discovery as configurable first phase and enhancement as unified pipeline.

cmd/auto_enhance.go

@@ -53,11 +53,11 @@ func runAutoEnhance(cmd *cobra.Command, args []string) error {
 	}
 	fmt.Printf("\n")
 
-	// Create auto enhancer
-	enhancer := content.NewAutoEnhancer()
+	// Create discoverer
+	discoverer := content.NewDiscoverer()
 
-	// Run auto enhancement
-	result, err := enhancer.EnhanceDirectory(inputDir, autoEnhanceOutput, autoEnhanceAggressive)
+	// Run element discovery
+	result, err := discoverer.DiscoverDirectory(inputDir, autoEnhanceOutput, autoEnhanceAggressive)
 	if err != nil {
 		return fmt.Errorf("auto-enhancement failed: %w", err)
 	}