Replace 6 stubbed test implementations with fully functional tests that validate:
- read_relay_state() returns correctly mocked state
- write_relay_state() updates internal mocked state
- read_all_states() returns 8 relays in known state
- Independent relay state management for all 8 channel indices
- Thread-safe concurrent state access with Arc<Mutex<>>
Tests now pass after T029-T031 completed MockRelayController implementation.
TDD phase: GREEN - tests validate implementation
Ref: T032 (specs/001-modbus-relay-control/tasks.md)
phundrak
1842ca25e3
