feat: Add 250-character limit validation for username input with comprehensive feedback#4

kertal with Copilot wants to merge 3 commits into

experiment-github-agentkertal/git-vegas:experiment-github-agentfrom

copilot/fix-bf8b167e-52c6-4527-95fa-cc9d5da4eefckertal/git-vegas:copilot/fix-bf8b167e-52c6-4527-95fa-cc9d5da4eefcCopy head branch name to clipboard