Constant MEMORY_DIFF_TOOL 

pub(crate) const MEMORY_DIFF_TOOL: &str = r#"{
  "name": "MemoryDiff",
  "description": "Show a line-based diff between two recorded versions of a memory file. Get version ids from MemoryHistory.",
  "inputSchema": {
    "type": "object",
    "properties": {
      "from_version_id": { "type": "string", "description": "The earlier version id (from MemoryHistory)" },
      "to_version_id":   { "type": "string", "description": "The later version id (from MemoryHistory)" }
    },
    "required": ["from_version_id", "to_version_id"]
  }
}"#;