feat(command-zone): add state machine with tests

Implement CommandZoneState - a pure C++ state machine managing zone
visibility transitions (Hidden, Revealed, Peeking states).

The state machine is intentionally decoupled from Qt graphics:
- Pure logic with no Qt dependencies in the state class
- Testable in isolation without a GUI
- Clear state transition table with StateChangeResult outcomes

Test coverage verifies:
- Initial state is Hidden
- Valid transitions: Hidden->Revealed, Hidden->Peeking, etc.
- Invalid transitions return NoChange
- Peek timeout triggers return to previous state

This establishes the foundation for command zone visibility management
while keeping graphics concerns separate.

cockatrice/CMakeLists.txt

@@ -103,6 +103,7 @@ set(cockatrice_SOURCES
     src/game/player/player_target.cpp
     src/game/replay.cpp
     src/game/zones/card_zone.cpp
+    src/game/zones/command_zone_state.cpp
     src/game/zones/hand_zone.cpp
     src/game/zones/logic/card_zone_logic.cpp
     src/game/zones/logic/hand_zone_logic.cpp