feat(citygen): flavor pack and theme table

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

crates/citygen/src/lib.rs

@@ -1,18 +1,22 @@
 //! World model and generator for the cyberpunk city.
 
+pub mod flavor;
 pub mod geom;
 pub mod ids;
 pub mod net;
 pub mod params;
 pub mod rng;
+pub mod theme;
 pub mod tile;
 pub mod validate;
 pub mod world;
 
+pub use flavor::FlavorPack;
 pub use geom::{Dir, Grid, Pos, Rect, Size};
 pub use ids::*;
 pub use net::*;
 pub use params::*;
+pub use theme::*;
 pub use tile::*;
 pub use validate::*;
 pub use world::*;