New comparison feature.

modules/story.py

@@ -66,6 +66,57 @@ def refresh_style_guidelines(model, folder=None):
         utils.log("SYSTEM", f"Failed to refresh guidelines: {e}")
     return current
 
+def merge_selected_changes(original, draft, selected_keys):
+    """Helper to merge specific fields from draft to original bible."""
+    # Sort keys to ensure deterministic order
+    def sort_key(k):
+        return [int(p) if p.isdigit() else p for p in k.split('.')]
+    selected_keys.sort(key=sort_key)
+
+    for key in selected_keys:
+        parts = key.split('.')
+        
+        # Metadata: meta.title
+        if parts[0] == 'meta' and len(parts) == 2:
+            field = parts[1]
+            if field == 'tone':
+                original['project_metadata']['style']['tone'] = draft['project_metadata']['style']['tone']
+            elif field in original['project_metadata']:
+                original['project_metadata'][field] = draft['project_metadata'][field]
+                
+        # Characters: char.0
+        elif parts[0] == 'char' and len(parts) >= 2:
+            idx = int(parts[1])
+            if idx < len(draft['characters']):
+                if idx < len(original['characters']):
+                    original['characters'][idx] = draft['characters'][idx]
+                else:
+                    original['characters'].append(draft['characters'][idx])
+                    
+        # Books: book.1.title
+        elif parts[0] == 'book' and len(parts) >= 2:
+            book_num = int(parts[1])
+            orig_book = next((b for b in original['books'] if b['book_number'] == book_num), None)
+            draft_book = next((b for b in draft['books'] if b['book_number'] == book_num), None)
+            
+            if draft_book:
+                if not orig_book:
+                    original['books'].append(draft_book)
+                    original['books'].sort(key=lambda x: x.get('book_number', 999))
+                    continue
+
+                if len(parts) == 2:
+                    orig_book['title'] = draft_book['title']
+                    orig_book['manual_instruction'] = draft_book['manual_instruction']
+                
+                elif len(parts) == 4 and parts[2] == 'beat':
+                    beat_idx = int(parts[3])
+                    if beat_idx < len(draft_book['plot_beats']):
+                        while len(orig_book['plot_beats']) <= beat_idx:
+                            orig_book['plot_beats'].append("")
+                        orig_book['plot_beats'][beat_idx] = draft_book['plot_beats'][beat_idx]
+    return original
+
 def filter_characters(chars):
     """Removes placeholder characters generated by AI."""
     blacklist = ['name', 'character name', 'role', 'protagonist', 'antagonist', 'love interest', 'unknown', 'tbd', 'todo', 'hero', 'villain', 'main character', 'side character']