Dev tool: switch player class (Warrior/Ranger) at runtime for testing

Editor-only class swap via the existing scalar dev-RPC family (new DebugOp.SetClass): F1/F2 keybind (ClassSwitchHotkeySystem), DebugOverlay '- Class -' buttons, and DebugCommandSendSystem.SetWarrior/SetRanger/SetClass statics. Server (DebugCommandReceiveSystem) swaps class in place on the spawned player: strips+re-seeds the ClassTraits StatModifier seeds, swaps the AbilityRef Fire slot, resets the ability cooldown, and heals a LIVING player to the new max (dead players skip the heal so respawn isn't raced). Server-authoritative + prediction-correct (same buffer-mutation path as GrantUpgrade); wire type unchanged so the RpcCollection hash is unaffected.

ClassTraits gains a shared Seeds core (spawn + swap can't drift), ClassSeedCount, IsClassSeed, a DynamicBuffer AppendSeeds overload, and Reapply. +3 EditMode tests (exact-count round-trip, value-equality fold, boundary/foreign-mod preservation); 351/351 green; Warrior<->Ranger round-trip Play-validated (server+client agree).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Project/Scripts/Simulation/Debug/DebugCommandRequest.cs

@@ -63,5 +63,10 @@ namespace ProjectM.Simulation
 
         /// <summary>Set the <see cref="TuningKnob"/> ArgA to ArgB/1000f (live dash/Charger feel-tuning; MC-0).</summary>
         public const byte SetTuning = 12;
+
+        /// <summary>Swap the sender's class to ArgA (a <see cref="CharacterId"/> byte: Warrior=2 / Ranger=3).
+        /// Strips the old class trait seeds, re-seeds the new ones, swaps the Fire ability, and heals a living
+        /// player to the new class's max. Editor-only dev tool (class-switch); 0 / unknown -> Warrior.</summary>
+        public const byte SetClass = 13;
     }
 }