chore: ignore .claude/plans/ directory

Add .claude/plans/ to .gitignore to exclude AI-generated planning
drafts from version control. These are temporary session files that
don't need to be shared with the team.

Author: LessUp

.gitignore

@@ -60,3 +60,6 @@ _bmad-output/
 
 # Git worktrees
 .worktrees/
+
+# Claude Code plans (AI-generated planning drafts)
+.claude/plans/