Validate Nested Markup Tags

Problem

Given a string markup containing only the characters <, >, /, lowercase letters, and spaces, determine whether it is a valid nested tag sequence. A valid tag is either an opening tag like <ride> or a closing tag like </ride>. Tags must be properly nested and matched in order. Return True if the full string is valid, otherwise return False.

Constraints

• 1 <= len(markup) <= 10^5
• Tag names contain only lowercase English letters and have length at least 1
• The input contains only <, >, /, lowercase letters, and spaces
• Text outside tags is not allowed except spaces between tags