Attribute Macro fsm 

#[fsm]

FR157: mark an FSM state enum so variant names become a label set.

Optional attribute: name = "demo" overrides the FSM id (default: type name). Only unit variants are supported. Empty enums / non-enums → compile_error!.

Implements [bitloom_prelude::FsmLabels]. Re-exported as #[rhdl::fsm] / #[bitloom::fsm] from bitloom-prelude (AD-6).