Hygiene B2: dead-code removal

Delete (unreferenced in any scene, per operator decision):
- TrainingDummy* chain (authoring/spawner/system/components/prefab) + UpgradePickup* chain (authoring/spawner/systems/components/prefab); remove TrainingDummyTag from the 3 live combat queries (AbilityFire/Melee/HealthApplyDamage now key on EnemyTag) and repoint HealthApplyDamageSystemTests to EnemyTag.
- Dead RPC RegionTransitSystem + RegionTransitRequest (no sender, ungated) + its test.
- Heartbeat + HeartbeatSystem (no WorldSystemFilter, ran no-op every tick) + its test.
- BuildSendSystem dead conveyor/pylon dev hooks (s_ConveyorDir, [/] rotation, Place{Pylon,Harvester,Conveyor} statics).
- Deprecated CyclePhase alias consts (Expedition/Defend/Build/*Ticks); repoint WaveSystemTests to Siege/Calm.
- Unread FeelConfig fields (HitFlashDurationMs, RumbleHeavy) + dangling HudUi doc-comments + stale crefs.

451/451 EditMode tests pass. CLAUDE.md HeartbeatSystemTests example ref to be repointed in B7.

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

Assets/_Project/Scripts/Simulation/World/CycleComponents.cs

@@ -39,22 +39,6 @@ namespace ProjectM.Simulation
         /// <summary>The base is under assault by a Husk wave (event-triggered; ends when the wave is cleared).</summary>
         public const byte Siege = 1;
 
-        // ---- Deprecated aliases (kept so HUD/audio/tests keep compiling through the cut-over; cleaned up later). ----
-
-        /// <summary>DEPRECATED alias of <see cref="Calm"/>.</summary>
-        public const byte Expedition = 0;
-
-        /// <summary>DEPRECATED alias of <see cref="Siege"/>.</summary>
-        public const byte Defend = 1;
-
-        /// <summary>DEPRECATED, unreachable — the timed Build phase is retired.</summary>
-        public const byte Build = 2;
-
-        /// <summary>DEPRECATED — the forced Expedition timer is retired (the loop is player-driven). Kept so existing crefs resolve.</summary>
-        public const uint ExpeditionTicks = 3600;
-
-        /// <summary>DEPRECATED — the forced Build timer is retired. Kept so existing crefs resolve.</summary>
-        public const uint BuildTicks = 1200;
     }
 
     /// <summary>