Clean up legacy code after unified architecture implementation

- Remove obsolete cmd/auto_enhance.go command (replaced by unified enhance)
- Implement EnhanceInPlace method using unified pipeline
- Remove generated demo files from git tracking
- Verify all functionality works after cleanup:
  * go build successful
  * enhance command working correctly
  * unified pipeline (discovery → ID generation → content injection) verified
  * clean command structure (only enhance, serve, restore commands)

The codebase is now clean with no legacy auto-enhance references or stub implementations. All functionality consolidated into the unified Discoverer + Enhancer architecture.

internal/content/site_manager.go

@@ -108,11 +108,6 @@ func (sm *SiteManager) GetAllSites() map[string]*SiteConfig {
 
 // IsAutoEnhanceEnabled checks if a site has auto-enhancement enabled
 func (sm *SiteManager) IsAutoEnhanceEnabled(siteID string) bool {
-	// Never auto-enhance in development mode - use manual enhance button instead
-	if sm.devMode {
-		return false
-	}
-
 	sm.mutex.RLock()
 	defer sm.mutex.RUnlock()