Builds a Claude Code statusline from scratch or extends an existing one. A statusline is a live status bar that runs a shell script after every Claude response and displays data — security scans, git status, API quotas, build state — directly in the session. Use this skill when the user says "create a statusline", "make a statusline for X", "add X to my statusline", "show Y in the status bar", "build a statusline plugin", or "I want live data in my Claude session". Trigger even if the user just describes wanting live feedback during a Claude session without naming "statusline" explicitly. The skill drives from idea to a working, installed, tested statusline without requiring the user to direct every step.