feat: Complete HTML-first architecture implementation with API integration

- Replace value field with html_content for direct HTML storage
- Add original_template field for style detection preservation
- Remove all markdown processing from injector (delete markdown.go)
- Fix critical content extraction/injection bugs in engine
- Add missing UpdateContent PUT handler for content persistence
- Fix API client field names and add updateContent() method
- Resolve content type validation (only allow text/link types)
- Add UUID-based ID generation to prevent collisions
- Complete first-pass processing workflow for unprocessed elements
- Verify end-to-end: Enhancement → Database → API → Editor → Persistence

All 37 files updated for HTML-first content management system.
Phase 3a implementation complete and production ready.

internal/engine/engine.go

@@ -17,14 +17,17 @@ type ContentEngine struct {
 	idGenerator  *IDGenerator
 	client       ContentClient
 	authProvider *AuthProvider
+	injector     *Injector
 }
 
 // NewContentEngine creates a new content processing engine
 func NewContentEngine(client ContentClient) *ContentEngine {
+	authProvider := &AuthProvider{Type: "mock"} // default
 	return &ContentEngine{
 		idGenerator:  NewIDGenerator(),
 		client:       client,
-		authProvider: &AuthProvider{Type: "mock"}, // default
+		authProvider: authProvider,
+		injector:     NewInjector(client, ""), // siteID will be set per operation
 	}
 }
 
@@ -37,6 +40,7 @@ func NewContentEngineWithAuth(client ContentClient, authProvider *AuthProvider)
 		idGenerator:  NewIDGenerator(),
 		client:       client,
 		authProvider: authProvider,
+		injector:     NewInjectorWithAuth(client, "", authProvider), // siteID will be set per operation
 	}
 }
 
@@ -84,6 +88,20 @@ func (e *ContentEngine) ProcessContent(input ContentInput) (*ContentResult, erro
 
 		// Add/update content attributes to the node
 		e.addContentAttributes(elem.Node, id, elem.Type)
+
+		// Store content and template for newly discovered elements (first-pass)
+		if wasGenerated && (input.Mode == Enhancement || input.Mode == ContentInjection) {
+			// Extract content and template from the unprocessed element
+			htmlContent := e.extractHTMLContent(elem.Node)
+			originalTemplate := e.extractOriginalTemplate(elem.Node)
+
+			// Store in database via content client
+			_, err := e.client.CreateContent(input.SiteID, id, htmlContent, originalTemplate, elem.Type, "system")
+			if err != nil {
+				// Log error but don't fail the enhancement - content just won't be stored
+				fmt.Printf("⚠️ Failed to store content for %s: %v\n", id, err)
+			}
+		}
 	}
 
 	// 4. Inject content if required by mode
@@ -157,7 +175,7 @@ func (e *ContentEngine) determineContentType(node *html.Node) string {
 	case "h1", "h2", "h3", "h4", "h5", "h6":
 		return "text"
 	case "p", "div", "section", "article", "span":
-		return "markdown"
+		return "text"
 	default:
 		return "text"
 	}
@@ -211,28 +229,35 @@ func (e *ContentEngine) injectContent(elements []ProcessedElement, siteID string
 
 		if contentItem != nil {
 			// Inject the content into the element
-			elem.Content = contentItem.Value
-			e.injectContentIntoNode(elem.Node, contentItem.Value, contentItem.Type)
+			elem.Content = contentItem.HTMLContent
+
+			// Update injector siteID for this operation
+			e.injector.siteID = siteID
+			e.injector.injectHTMLContent(elem.Node, contentItem.HTMLContent)
 		}
 	}
 	return nil
 }
 
-// injectContentIntoNode injects content value into an HTML node
-func (e *ContentEngine) injectContentIntoNode(node *html.Node, content, contentType string) {
-	// Clear existing text content
-	for child := node.FirstChild; child != nil; {
-		next := child.NextSibling
-		if child.Type == html.TextNode {
-			node.RemoveChild(child)
+// extractHTMLContent extracts the inner HTML content from a node
+func (e *ContentEngine) extractHTMLContent(node *html.Node) string {
+	var content strings.Builder
+
+	// Render all child nodes in order to preserve HTML structure
+	for child := node.FirstChild; child != nil; child = child.NextSibling {
+		if err := html.Render(&content, child); err == nil {
+			// All nodes (text and element) rendered in correct order
 		}
-		child = next
 	}
 
-	// Add new text content
-	textNode := &html.Node{
-		Type: html.TextNode,
-		Data: content,
-	}
-	node.AppendChild(textNode)
+	return strings.TrimSpace(content.String())
+}
+
+// extractOriginalTemplate extracts the outer HTML of the element (including the element itself)
+func (e *ContentEngine) extractOriginalTemplate(node *html.Node) string {
+	var buf strings.Builder
+	if err := html.Render(&buf, node); err != nil {
+		return ""
+	}
+	return buf.String()
 }