🐛 fix(platform): export module APIs

[zrr1999]

Summary

• make the platform-owned basic_cli.* foreign functions public so applications can import them
• align their signatures with current Spore core spellings (Str, (), List[Str], Option[Str])
• match print / eprint / read_line with the host's IoError failure surface

Validation

• cargo test --manifest-path host/Cargo.toml
• find examples src/basic_cli -name "*.sp" -type f | sort | xargs spore format
• find examples src/basic_cli -name "*.sp" -type f | sort | xargs -n 1 spore check
• find examples src/basic_cli -name "*.sp" -type f | sort | xargs -n 1 spore build
• temporary package build importing basic_cli.stdout

Notes

• this unblocks package-owned platform modules from being imported by project-mode applications after spore #85