Function generate_rust 

pub fn generate_rust(state: &ArchitectureState) -> String

Generate a complete Rust source file from architecture state.

The returned string can be written to src/generated_schema.rs. It contains:

• One <Name>Value struct per record (with Serialize / Deserialize)
• One <Name>Key enum per record (with #[derive(RecordKey)])
• A configure_schema<R>() function wiring all records into AimDbBuilder