refactor: Complete UI cleanup and simplify editor architecture

- Remove complex style preservation system from editor
- Simplify markdown conversion back to straightforward approach
- Remove StyleContext class and style-aware conversion methods
- Switch content type from 'html' back to 'markdown' for consistency
- Clean up editor workflow to focus on core markdown editing
- Remove ~500 lines of unnecessary style complexity

This completes the UI unification cleanup by removing the overly complex
style preservation system that was making the editor harder to maintain.

lib/src/core/editor.js

@@ -1,5 +1,4 @@
 import { InsertrFormRenderer } from '../ui/form-renderer.js';
-import { markdownConverter } from '../utils/markdown.js';
 
 /**
  * InsertrEditor - Content editing workflow and business logic
@@ -115,35 +114,16 @@ export class InsertrEditor {
         
         try {
             // Extract content value based on type
-            let markdownContent;
+            let contentValue;
             if (meta.element.tagName.toLowerCase() === 'a') {
                 // For links, save the text content (URL is handled separately if needed)
-                markdownContent = formData.text || formData;
+                contentValue = formData.text || formData;
             } else {
-                markdownContent = formData.text || formData;
-            }
-            
-            // Convert markdown to HTML with style preservation
-            let contentValue;
-            const contentType = this.determineContentType(meta.element);
-            
-            if (contentType === 'html') {
-                // Extract style context from original element and convert markdown to HTML
-                const { markdown, styleContext } = markdownConverter.htmlToMarkdownWithContext(meta.element.innerHTML, meta.element);
-                
-                if (styleContext && styleContext.hasPreservableContent) {
-                    // Convert markdown back to HTML with style preservation
-                    contentValue = markdownConverter.markdownToHtmlWithStyles(markdownContent, styleContext);
-                } else {
-                    // No styles to preserve, simple conversion
-                    contentValue = markdownConverter.markdownToHtml(markdownContent);
-                }
-            } else {
-                // For other content types (text, link), use markdown as-is
-                contentValue = markdownContent;
+                contentValue = formData.text || formData;
             }
             
             // Universal upsert - server handles ID extraction/generation from markup
+            const contentType = this.determineContentType(meta.element);
             const result = await this.apiClient.createContent(
                 contentValue, 
                 contentType, 
@@ -175,8 +155,8 @@ export class InsertrEditor {
             return 'link';
         }
         
-        // ALL text elements use HTML storage with markdown editing interface
-        return 'html';
+        // ALL text elements use markdown for consistent editing experience
+        return 'markdown';
     }
     
     handleCancel(meta) {