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/enhancer.go

@@ -194,9 +194,11 @@ func (e *Enhancer) enhanceWithEngine(htmlContent []byte, filePath string) ([]byt
 
 // EnhanceInPlace performs in-place enhancement of static site files
 func (e *Enhancer) EnhanceInPlace(sitePath string, siteID string) error {
-	// TODO: Implement in-place enhancement using the unified pipeline
-	fmt.Printf("📄 Enhancement requested for site %s at %s (unified pipeline implementation needed)\n", siteID, sitePath)
-	return nil
+	// Update the enhancer's site ID for this operation
+	e.siteID = siteID
+
+	// Use EnhanceDirectory with same input and output (in-place)
+	return e.EnhanceDirectory(sitePath, sitePath)
 }
 
 // copyFile copies a file from src to dst