Entity: an equipped item keeps the hardpoint it occupies

The placement rule (HardpointAt) already finds the one hardpoint an item lies
in at equip; TryEquip threw that answer away and eighteen readers recomputed it
from the item's origin cell, which need not lie in the hardpoint (Soul's
scenarios batch-4 P30). EquippedItem.Hardpoint now carries the answer, null for
Tool gear and the hull, and every origin-cell lookup reads it instead:
FireControl.ArcFor, the eleven weapon managers, EntityInstance, ShipInstance
and ActionGameManager's articulation grouping. Entity.Hardpoints[,] stays the
per-cell map for armour and display.

TryFindSpace's hardpoint search tries every origin the fit rule can accept,
including ones up and left of the hardpoint, so a design whose shape lacks its
origin cell is found wherever ItemFits would place it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/FireControl.cs

@@ -35,7 +35,7 @@ public static class FireControl
     // GameplaySettings.FiringArc. Zero on the hardpoint means "use the default," not "no arc."
     public static float ArcFor(EquippedItem item)
     {
-        var hardpoint = item.Entity.Hardpoints[item.Position.x, item.Position.y];
+        var hardpoint = item.Hardpoint;
         var arc = hardpoint?.FiringArc ?? 0f;
         return arc > 0 ? arc : item.ItemManager.GameplaySettings.FiringArc;
     }