Visibility 5: a fired gun is aimable and its same-design twin is not; fix stale reveal-ranking comment

Builds: yes (verified by the follow-up job).

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

tests/Aetheria.Shared.Tests/ContactRevealTests.cs

@@ -249,6 +249,33 @@ public sealed class ContactRevealTests : IDisposable
         Assert.Empty(e.RevealsOf(o)); // a ship is not told what it shows
     }
 
+    // ---- AFiredGunIsAimableAndItsTwinIsNot ----
+
+    // Two guns of one design: firing one makes that gun, and only that gun, something the observer can select and
+    // keep aimed at. The book is per item, not per design or per hardpoint type.
+    [Fact]
+    public void AFiredGunIsAimableAndItsTwinIsNot()
+    {
+        var e = Add(float3(30, 0, 40), new[] { "Gun", "Gun" });
+        var o = Add(float3(0, 0, 0), new[] { "Eye" });
+        var guns = Guns(e);
+        Assert.Same(guns[0].Data, guns[1].Data); // the same design
+        o.SetTarget(e);
+        Assert.False(FireControl.IsRevealed(o, guns[0]));
+        Assert.False(o.TrySelectTargetItem(guns[0]));
+
+        Fire(e, guns[0]);
+        o.SetTarget(e);
+
+        Assert.True(FireControl.IsRevealed(o, guns[0]));
+        Assert.False(FireControl.IsRevealed(o, guns[1]));
+        Assert.False(o.TrySelectTargetItem(guns[1]));
+        Assert.True(o.TrySelectTargetItem(guns[0]));
+        for (var i = 0; i < 300; i++) Tick(.1f);
+        Assert.Same(guns[0], o.ResolvedTargetItem);
+        Assert.False(FireControl.IsRevealed(o, guns[1]));
+    }
+
     // ---- AnActAboveTheReachRevealsNothing ----
 
     // Info settles at S x 2 / (d k): with S = 5 the act is revealed inside d = 100 / k and not beyond it, whatever k is.

tests/Aetheria.Shared.Tests/FireControlCut6dTests.cs

@@ -108,8 +108,8 @@ public sealed class FireControlCut6dTests : IDisposable
             } }
         });
         // Durability far above anything a single shot deals: an aim point this cut's tests fire hundreds or
-        // thousands of rounds at must survive being hit directly for the whole run, or Cut 5.5's "a destroyed
-        // item drops out of the reveal ranking" rule pulls the aim out from under later shots mid-sample and
+        // thousands of rounds at must survive being hit directly for the whole run, or a destroyed aim point is
+        // dropped from aiming (FireControl.IsRevealed) and pulls the aim out from under later shots mid-sample and
         // silently corrupts the landing distribution for everything fired after that point.
         cache.Upsert(new GearData
         {