Visibility 4a: retire the ping's light signature; Emission is never light

SetSignature refuses Emission; Sensor.PingVisibility (key 7) is retired and
Ping() writes no signature; Sense's Emission skip, the departure subtraction
and SignatureOn are deleted. Tests: SetSignatureRefusesEmission,
APingNoLongerBrightensThePinger; fixtures drop PingVisibility.

Not yet built or tested at this commit (verify job follows).

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

Assets/Scripts/ServerShared/Behaviors/Sensor.cs

@@ -24,8 +24,7 @@ public class SensorData : BehaviorData
     [Inspectable, JsonProperty("pingEnergy"), Key(6), RuntimeInspectable]
     public PerformanceStat PingEnergy;
 
-    [Inspectable, JsonProperty("pingVisibility"), Key(7), RuntimeInspectable]
-    public PerformanceStat PingVisibility;
+    // Key 7 (pingVisibility) is retired: never reuse it.
 
     [Inspectable, JsonProperty("pingRange"), Key(8), RuntimeInspectable]
     public PerformanceStat PingRange;
@@ -137,7 +136,6 @@ public class Sensor : Behavior, IEventBehavior, IPowerConsumer
         // nothing would ever fill this capacitor; bypass it rather than starving such an instance forever.
         if(_pingCooldown < 0 && (Item == null || _capacitor.TrySpend(_capacitor.Capacity)))
         {
-            Entity.SetSignature(this, SignatureChannel.Emission, Evaluate(_data.PingVisibility), Item); // interim: emissions-heard replaces this with a range-gated emission
             _pinging = true;
             _pingZone = Entity.Zone;
             _pingCooldown = 1;

Assets/Scripts/ServerShared/Entity.cs

@@ -93,9 +93,14 @@ public abstract class Entity
     public IReadOnlyDictionary<object, Signature> VisibilitySources => _visibilityView ??= new ReadOnlyDictionary<object, Signature>(_visibilitySources);
 
     // The one writer of VisibilitySources (the decay loop in Update is the one decayer). Every light signature
-    // names its channel and the item that produced it (null for the hull).
-    public void SetSignature(object source, SignatureChannel channel, float strength, EquippedItem item) =>
+    // names its channel and the item that produced it (null for the hull). Emission is active emission (paints now,
+    // Entity.Emit after emissions-heard), never light: ruling visibility-per-capability-reveal, map R1.
+    public void SetSignature(object source, SignatureChannel channel, float strength, EquippedItem item)
+    {
+        if (channel == SignatureChannel.Emission)
+            throw new ArgumentException("Emission is active emission, never a light signature.", nameof(channel));
         _visibilitySources[source] = new Signature(channel, strength, item);
+    }
     public readonly ReactiveDictionary<Entity, float> EntityInfoGathered = new ReactiveDictionary<Entity, float>();
 
     public (List<Weapon> weapons, List<EquippedItem> items)[] WeaponGroups;
@@ -169,8 +174,6 @@ public abstract class Entity
     public int AssignedPopulation => PopulationAssignments.Sum(pa => pa.AssignedPopulation);
     public float Mass { get; private set; }
     public float Visibility => VisibilitySources.Values.Sum(s => s.Strength);
-    public float SignatureOn(SignatureChannel channel) =>
-        VisibilitySources.Values.Where(s => s.Channel == channel).Sum(s => s.Strength);
 
     public Subject<Entity> IncomingHit = new Subject<Entity>();
     public Subject<(int2 pos, float damage)> ArmorDamage = new Subject<(int2, float)>();
@@ -952,7 +955,7 @@ public abstract class Entity
     // What this observer's instruments receive of other ships' acts this tick (Zone.Update calls it once, after every
     // entity has updated): every light signature of an item that would alone settle this observer's passive info above
     // TargetDetectionInfoThreshold is revealed (ruling visibility-per-capability-reveal). Hull radiation names no
-    // item and only feeds the track; an Emission entry is never light. One PassiveInfo per ship. Zone.Update calls it
+    // item and only feeds the track. One PassiveInfo per ship. Zone.Update calls it
     // for every entity after all of them have updated, so what a ship shows is what every observer receives on that
     // tick whatever order the zone lists them in.
     internal void Sense()
@@ -967,7 +970,7 @@ public abstract class Entity
             var perSignature = -1f;
             foreach (var signature in other._visibilitySources.Values)
             {
-                if (signature.Item == null || signature.Channel == SignatureChannel.Emission) continue;
+                if (signature.Item == null) continue;
                 if (perSignature < 0f) perSignature = PassiveInfo(other.Position.xz, 1f);
                 if (signature.Strength * perSignature > threshold) RecordReveal(other, signature.Item, signature.Channel);
             }

Assets/Scripts/ServerShared/Sensing.cs

@@ -94,7 +94,7 @@ public readonly struct Reveal
 }
 
 // A subject's removal from a zone as the zone recorded it (death, dock, warp, any removal): where it was and how
-// bright its light was (its signature outside the Emission channel). Judged by each observer's Sense under the
+// bright its light was (its Visibility at removal). Judged by each observer's Sense under the
 // light-act gate; notification only, one tick long, it decides nothing.
 public readonly struct Departure
 {

Assets/Scripts/ServerShared/Zone.cs

@@ -114,7 +114,7 @@ public class Zone
         Entities.ObserveAdd().Subscribe(add => add.Value.Death.Subscribe(_ => { Entities.Remove(add.Value); add.Value.Deactivate(); }));
         // The one record of a removal for observers (ruling reveal-ends-on-perception): read by the next Sense pass.
         Entities.ObserveRemove().Subscribe(remove => _departures.Add(new Departure(remove.Value, remove.Value.Position.xz,
-            remove.Value.Visibility - remove.Value.SignatureOn(SignatureChannel.Emission))));
+            remove.Value.Visibility)));
 
         Targets.Add(new EntityTargets());