chore: ignore Claude/skill artifacts in .gitignore

Add Claude/skill artifact patterns (.claude/, .superpowers/, docs/superpowers/, CLAUDE.md, progress-tracker.md, REQUIREMENTS.md, .worktrees/) to keep local AI/editor scratch out of git.

Author: sunilp

.gitignore

@@ -11,3 +11,7 @@ docs/superpowers/
 CLAUDE.md
 progress-tracker.md
 REQUIREMENTS.md
+
+# Local AI/editor agent config — never commit Claude/skill artifacts
+.superpowers/
+.worktrees/