refactor: util.parseArgs + slingshot actorResolver, drop 2 deps
- replace hand-rolled if-else CLI parser with node:util parseArgs
- replace identity-resolver packages with inline slingshot actorResolver
- drop @atcute/identity-resolver and @atcute/identity-resolver-node
- remove unused SCOPE constant
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>