fix(text_editor.py): update error message for content hash mismatch to provide clearer instructions for appending content

Author: tumf

src/mcp_text_editor/text_editor.py

@@ -396,7 +396,7 @@ async def edit_file_contents(
                         if actual_range_hash != expected_range_hash:
                             return {
                                 "result": "error",
-                                "reason": f"Content hash mismatch - file has been modified since last read. Please use get_text_file_contents tool with lines {line_start}-{line_end} to get current content and hashes, then retry with the updated hashes. Expected: {expected_range_hash}, Actual: {actual_range_hash}. Content: {target_content!r}",
+                                "reason": f"Content hash mismatch - file has been modified since last read. Please use get_text_file_contents tool with lines {line_start}-{line_end} to get current content and hashes, then retry with the updated hashes. If you want to append content, set line_start to {len(lines)+1}.",
                                 "file_hash": None,
                                 "content": current_content,
                             }