Performs exact string replacement in a file. - You must ${READ_TOOL_NAME} the file in this conversation before editing, or the call will fail. - `old_string` must match the file exactly, including indentation, and be unique — the edit fails otherwise. Strip the Read line prefix (${SUPPORTS_COLON_LINE_PREFIX?"line number + a single tab or `:`":"line number + tab"}) before matching. - `replace_all: true` replaces every occurrence instead.