chore: update magic_cli — install command overhaul complete

- install_stubs.dart: 15 static String methods for all generated files
- install_command.dart: full rewrite, 7 --without-* flags, main.dart replacement
- TDD: 40/40 tests pass, dart analyze clean
- Generates: 7 configs, welcome_view, kernel.dart, .env, routes/app.dart
- Idempotent, E2E verified with dart analyze 0 issues on generated project

Author: anilcancakir