fix(main): untrack local skill tooling, fmt, requireAdmin asserts predicate

- repo:hygiene: git rm --cached the .agents/.codebuddy/.grok/.trae/.zcode/
  skills/ skills-lock.json entries that were tracked AND gitignored (installed
  via npx skills add; user-local only).
- fmt: deno fmt after the merge-fleet conflict resolutions.
- examples:check: requireAdmin gains 'asserts user is AuthenticatedIdentity'
  so admin.tsx's user.id reads type-narrow after the notFound() guard (#1047
  conflict resolution kept HEAD's notFound channel but dropped the predicate).

Author: DevBot