Scaffold flag parity (`--template/--addons/--extend/--set/--force/--no-install`)

[ulises-jeremias]

Summary

Implement all scaffold-related flags from CNA CLI.

CNA mapping

CNA: options in src/index.ts lines ~104–176.

Acceptance criteria

• Each flag documented in --help
• Integration tests cover template + addons + extend + set
• --force allows non-empty dirs

Blocked by

none

Blocks

none

Reference

Parity matrix (workspace): knowledge/create-python-app-parity-matrix.md
Reference repo: https://github.com/Create-Node-App/create-node-app

Parent epic

#5