[Game] Add Command Zone support with commander tax tracking

- Add CommandZone and CommandZoneLogic for commander
  - Add CommanderTaxCounter
  - Add counter active state protocol (show/hide tax counters)
  - Add "Enable Command Zone" option in game creation dialogs
  - Add context menu actions for command zone operations

Took 9 minutes

Took 11 minutes

libcockatrice_utility/CMakeLists.txt

@@ -18,6 +18,7 @@ set(UTILITY_HEADERS
     libcockatrice/utility/string_limits.h
     libcockatrice/utility/dice_limits.h
     libcockatrice/utility/counter_limits.h
+    libcockatrice/utility/counter_ids.h
     libcockatrice/utility/clamped_arithmetic.h
     libcockatrice/utility/zone_names.h
     libcockatrice/utility/days_years_between.h

libcockatrice_utility/libcockatrice/utility/counter_ids.h

@@ -0,0 +1,46 @@
+/**
+ * @file counter_ids.h
+ * @ingroup GameLogic
+ * @brief Shared counter IDs and names for system counters (e.g. commander tax).
+ */
+
+#ifndef COCKATRICE_COUNTER_IDS_H
+#define COCKATRICE_COUNTER_IDS_H
+
+#include <QString>
+
+/**
+ * Shared counter IDs used by both client and server.
+ * These must match between server_player.cpp and player_event_handler.cpp.
+ *
+ * Reserved counter IDs for system counters:
+ *   IDs 0-7:  Standard player counters (life, mana colors, storm)
+ *   IDs 8-9:  Commander tax counters
+ *   IDs 10+:  Available for user-created counters
+ *
+ * The server's newCounterId() starts from the highest existing ID + 1,
+ * so these reserved IDs won't conflict as long as they're created first
+ * during setupZones(). See server_player.cpp::setupZones() for the
+ * authoritative list of reserved IDs.
+ *
+ * To find all files referencing these IDs, grep for CounterIds::CommanderTax
+ * and CounterIds::PartnerTax across the codebase.
+ */
+namespace CounterIds
+{
+constexpr int CommanderTax = 8;
+constexpr int PartnerTax = 9;
+} // namespace CounterIds
+
+namespace CounterNames
+{
+constexpr const char *CommanderTax = "commander_tax_counter";
+constexpr const char *PartnerTax = "partner_tax_counter";
+
+inline bool isTaxCounter(const QString &name)
+{
+    return name == CommanderTax || name == PartnerTax;
+}
+} // namespace CounterNames
+
+#endif // COCKATRICE_COUNTER_IDS_H

libcockatrice_utility/libcockatrice/utility/zone_names.h

@@ -14,6 +14,9 @@ constexpr const char *DECK = "deck";
 constexpr const char *SIDEBOARD = "sb";
 constexpr const char *STACK = "stack";
 
+// Command zone (Commander format)
+constexpr const char *COMMAND = "command";
+
 } // namespace ZoneNames
 
 #endif // ZONE_NAMES_H