docs(server.py): update description for range_hash to clarify its purpose and usage in the EditTextFileContentsHandler class

Author: tumf

src/mcp_text_editor/server.py

@@ -140,7 +140,7 @@ def get_tool_description(self) -> Tool:
                                             "contents": {"type": "string"},
                                             "range_hash": {
                                                 "type": "string",
-                                                "description": "Hash of the content being replaced (required except for new files and append operations)",
+                                                "description": "Hash of the content being replaced from line_start to line_end (required except for new files and append operations)",
                                             },
                                         },
                                         "required": ["contents"],