a7a7e7ef18
Created test suite for Relay entity covering construction, state toggling, and explicit state control methods. Tests intentionally fail as Relay struct is not yet implemented. Tests cover: - Relay::new() with id, state, and optional label - toggle() flipping state between On/Off - turn_on() setting state to On - turn_off() setting state to Off TDD phase: RED - Tests written, implementation pending (T022) Ref: T021 (specs/001-modbus-relay-control/tasks.md)