fix: resolve markdown roundtrip formatting issue in save functionality

Fixed critical bug where saving unedited content would introduce unwanted
indentation and formatting changes due to unnecessary DOM reconstruction.

Problem:
- getMarkdownContent() always reconstructed from DOM elements
- textContent doesn't preserve original markdown formatting
- HTML rendering adds/removes whitespace causing formatting drift
- Lines after first would get extra indentation on roundtrip

Solution:
- Added hasEdits tracking to MarkitectEditor class
- Return original markdown content when no edits have been made
- Only reconstruct from DOM when actual edits occurred
- Mark hasEdits=true when textarea blur event fires

This ensures perfect fidelity when saving unedited documents while
maintaining the reconstruction capability for edited content.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

markitect/document_manager.py

@@ -657,6 +657,7 @@ class DocumentManager:
             editor_scripts = """
         class MarkitectEditor {
             constructor() {
+                this.hasEdits = false; // Track if any edits have been made
                 this.initializeEditor();
                 this.setupKeyboardShortcuts();
             }
@@ -707,6 +708,7 @@ class DocumentManager:
                 textarea.className = 'edit-mode';
 
                 textarea.addEventListener('blur', () => {
+                    this.hasEdits = true; // Mark that edits have been made
                     section.innerHTML = marked.parse(textarea.value);
                     this.markSections(section.parentElement);
                 });
@@ -781,6 +783,11 @@ class DocumentManager:
             }
 
             getMarkdownContent() {
+                // If no edits have been made, return the original markdown content
+                if (!this.hasEdits) {
+                    return markdownContent;
+                }
+
                 // Reconstruct markdown content from the current state of sections
                 const content = document.getElementById('markdown-content');
                 if (!content) {