polish(fxa): Ignore claude work trees

Author: dschom

.gitignore

@@ -196,7 +196,4 @@ libs/shared/cms/src/__generated__/graphql.js
 .env.sentry-build-plugin
 
 # Anthropic's Claude AI — ignore everything except checked-in skills
-.claude
-!.claude/
-!.claude/skills/
-!.claude/skills/**
+.claude/worktrees