typub-core 0.1.0

Shared capability types and content model for typub.

This crate defines the canonical enum types for platform capabilities, asset strategies, theme identifiers, and the core content model.

Per [[ADR-0002]], extracting these types into a shared subcrate ensures:

• Single source of truth for enum variants
• Serde-based validation of TOML config at build time
• Type safety via ThemeId newtype for theme identifiers