Fix station docking bays, save-safe instance keys, and zero-weight draws

One rule now governs interior space: an empty hardpoint cell is usable, in
both UnoccupiedSpace and ItemFits. ItemFits used to refuse hardpoint cells
that UnoccupiedSpace offered, so stations failed to equip a docking bay.

CraftedItemInstance.Ingredients and Product move from keys 3 and 4 to 9 and
10, past every key the derived instances use. At 3 and 4 an older save reads
nil into a non-nullable Guid and fails to load.

WeightedRandomElements returns an empty array when every weight is zero,
instead of an array of nulls. LoadoutGenerator treats a missing Galaxy as
"every product available", the seam a fixture needs to generate loadouts
without a galaxy. ZoneGenerator skips a story station that fails to generate
and logs it, instead of throwing.

Verified: Aetheria.Shared and tools/AetherDb build headless; Unity 6000.3.24f1
batchmode compile succeeds; AetherDb doctor, station-fit and loadout pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/Entity.cs

@@ -532,13 +532,11 @@ public abstract class Entity
             // Check every cell of the item's shape
             foreach (var i in itemData.Shape.Coordinates)
             {
-                // If there is any gear already occupying that space, it won't fit
-                // If there's a hardpoint there, it won't fit
-                // Thermal items have their own layer and do not collide with gear
+                // An interior cell is usable when no gear occupies it. An empty hardpoint cell counts as usable:
+                // general gear may take it until hardpoint gear claims it, which is the same rule
+                // UnoccupiedSpace reports, so what generation is offered and what equipping accepts agree.
                 var itemCoord = hullCoord + itemData.Shape.Rotate(i, item.Rotation);
-                if (!hullData.InteriorCells[itemCoord] || 
-                    itemData.HardpointType == HardpointType.Tool && Hardpoints[itemCoord.x, itemCoord.y] != null || 
-                    GearOccupancy[itemCoord.x, itemCoord.y] != null) 
+                if (!hullData.InteriorCells[itemCoord] || GearOccupancy[itemCoord.x, itemCoord.y] != null)
                     return false;
             }
         }

Assets/Scripts/ServerShared/Extensions.cs

@@ -34,6 +34,10 @@ public static class Extensions
             totalWeight += weights[x];
         }
 
+        // Nothing can be drawn from a set whose weights all come to nothing. Returning an empty array says so,
+        // where a full array of unset elements would read as "found these" and hand the caller nulls.
+        if (totalWeight <= 0) return new T[0];
+
         var randomElements = new T[count];
         for (int i = 0; i < count; i++)
         {

Assets/Scripts/ServerShared/ItemInstance.cs

@@ -37,12 +37,16 @@ public abstract class CraftedItemInstance : ItemInstance
     // The workmanship of this particular unit, as distinct from the parts that went into it.
     [JsonProperty("quality"), Key(2)]  public float Quality;
 
-    // The part filling each of the design's roles, one level deep. Empty on items made before roles existed,
-    // and on parts themselves; stats then read Quality as they always did.
-    [JsonProperty("ingredients"), Key(3)]  public List<RoleFill> Ingredients = new List<RoleFill>();
+    // Keys 9 and 10, past every key the derived instances use: an item saved before these existed has no
+    // element there at all. Keys 3 to 6 sit inside the old range and read back as nil, which a non-nullable
+    // Guid cannot deserialize, so nothing new may go there.
+
+    // How good the part filling each of the design's roles turned out. Empty on items made before roles
+    // existed; stats then read Quality as they always did.
+    [JsonProperty("ingredients"), Key(9)]  public List<RoleFill> Ingredients = new List<RoleFill>();
 
     // The manufacturer's branded product this was built as, naming it and carrying its flavor text.
-    [JsonProperty("product"), Key(4)]  public Guid Product;
+    [JsonProperty("product"), Key(10)]  public Guid Product;
 
     // The quality a stat reads for one of the design's roles. An unnamed role, a design without roles, and an
     // item built before roles existed all fall back to this item's own workmanship.

Assets/Scripts/ServerShared/LoadoutGenerator.cs

@@ -146,14 +146,16 @@ public class LoadoutGenerator
             count);
     }
 
+    // No galaxy means no availability to filter by: every product is on offer. A fixture generates loadouts that
+    // way, so a test can exercise placement and products without standing up a whole galaxy; no game path does.
     private bool IsAvailable(FactionProductData product) =>
-        Galaxy.IsPrelude ||
+        Galaxy == null || Galaxy.IsPrelude ||
         Galaxy.ContainsFaction(product.Manufacturer) && (Faction == null || Faction.Allegiance.ContainsKey(product.Manufacturer));
 
     // Prioritize products from the zone faction and its allies, penalizing distance to the manufacturer's headquarters
     private float ManufacturerPreference(Guid manufacturer)
     {
-        if (Faction == null) return 1;
+        if (Faction == null || Galaxy == null) return 1;
         var allegiance = manufacturer == Faction.ID ? 1 :
             Faction.Allegiance.TryGetValue(manufacturer, out var a) ? a : 0;
         var home = Galaxy.HomeZones.FirstOrDefault(h => h.Key.ID == manufacturer).Value;

Assets/Scripts/ServerShared/ZoneGenerator.cs

@@ -296,6 +296,11 @@ public static class ZoneGenerator
 	        var orbit = selectedStationOrbits[i];
 	        var lagrangeOrbit = CreateLagrangeOrbit(orbit);
 	        var station = GetLoadoutGenerator(story.Faction).GenerateStationLoadout();
+	        if (station == null)
+	        {
+		        itemManager.Log($"Story station for {story.Faction?.Name} could not be generated; its story has nowhere to live!");
+		        continue;
+	        }
 	        station.Orbit = lagrangeOrbit.ID;
 	        station.SecurityLevel = story.Security;
 	        station.SecurityRadius = pack.Radius;