fix(render): harden portal exit handoff

tests/AcDream.Core.Tests/World/TeleportAnimSequencerTests.cs

@@ -168,6 +168,31 @@ public sealed class TeleportAnimSequencerTests
         Assert.Contains(TeleportAnimEvent.Place, evts);
     }
 
+    [Fact]
+    public void DiagnosticHold_KeepsReadyPortalInStableTunnelUntilReleased()
+    {
+        var seq = new TeleportAnimSequencer();
+        seq.Begin(TeleportEntryKind.Portal);
+
+        var (_, heldEvents) = seq.Tick(
+            dt: 30f,
+            worldReady: true,
+            tunnelAnimationFrame: 72,
+            holdInTunnel: true);
+
+        Assert.Equal(TeleportAnimState.Tunnel, seq.State);
+        Assert.DoesNotContain(TeleportAnimEvent.Place, heldEvents);
+
+        var (_, releasedEvents) = seq.Tick(
+            dt: 0f,
+            worldReady: true,
+            tunnelAnimationFrame: 72,
+            holdInTunnel: false);
+
+        Assert.Equal(TeleportAnimState.TunnelContinue, seq.State);
+        Assert.Contains(TeleportAnimEvent.Place, releasedEvents);
+    }
+
     // --- TunnelContinue: MIN_CONTINUE hold then TunnelFadeOut ---
 
     [Fact]
@@ -301,6 +326,44 @@ public sealed class TeleportAnimSequencerTests
             framesPerSecond);
     }
 
+    [Fact]
+    public void TunnelFadeOut_SwapsAfterLastFullViewportCaptureLevel()
+    {
+        Assert.Equal((short)1001, TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel);
+
+        var seq = new TeleportAnimSequencer();
+        seq.Begin(TeleportEntryKind.Portal);
+        seq.Tick(0f, worldReady: false);
+        seq.Tick(0.016f, worldReady: true);
+        seq.Tick(
+            TeleportAnimSequencer.MinContinue,
+            worldReady: true,
+            tunnelAnimationFrame: 72);
+        Assert.Equal(TeleportAnimState.TunnelFadeOut, seq.State);
+
+        float lastSafeTime = Enumerable.Range(0, 1001)
+            .Select(static i => i / 1000f)
+            .First(t => TeleportAnimSequencer.GetRetailAnimationLevel(t)
+                == TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel);
+        float firstUnsafeTime = Enumerable.Range(0, 1001)
+            .Select(static i => i / 1000f)
+            .First(t => TeleportAnimSequencer.GetRetailAnimationLevel(t)
+                > TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel);
+
+        var (lastSafe, _) = seq.Tick(lastSafeTime, worldReady: true);
+        Assert.Equal(TeleportAnimState.TunnelFadeOut, lastSafe.State);
+        Assert.Equal(
+            TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel / 1024f,
+            lastSafe.ViewPlaneBlend);
+
+        var (swapped, events) = seq.Tick(
+            firstUnsafeTime - lastSafeTime,
+            worldReady: true);
+        Assert.Equal(TeleportAnimState.WorldFadeIn, swapped.State);
+        Assert.False(swapped.ShowTunnel);
+        Assert.Contains(TeleportAnimEvent.PlayExitSound, events);
+    }
+
     private static void AssertOutgoingViewportRetiresBeforeTerminal(
         TeleportAnimSequencer seq,
         TeleportAnimState outgoingState,
@@ -314,7 +377,8 @@ public sealed class TeleportAnimSequencerTests
             if (snapshot.State == outgoingState)
             {
                 Assert.True(
-                    snapshot.ViewPlaneBlend <= 1022f / 1024f,
+                    snapshot.ViewPlaneBlend
+                        <= TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel / 1024f,
                     $"Published unsafe outgoing blend {snapshot.ViewPlaneBlend}.");
                 continue;
             }
@@ -384,8 +448,13 @@ public sealed class TeleportAnimSequencerTests
         seq.Begin(TeleportEntryKind.Logout);
         seq.Tick(0f, worldReady: false); // consume enter-sound tick, elapsed≈0
 
-        // Drive to just BEFORE the transition (so we're still in WorldFadeOut)
-        DriveSeconds(seq, TeleportAnimSequencer.FadeTime - 0.03f, worldReady: false);
+        float lastSafeTime = Enumerable.Range(0, 1001)
+            .Select(static i => i / 1000f)
+            .First(t => TeleportAnimSequencer.GetRetailAnimationLevel(t)
+                == TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel);
+
+        // Drive directly to the last full-viewport quantized table level.
+        seq.Tick(lastSafeTime, worldReady: false);
         Assert.Equal(TeleportAnimState.WorldFadeOut, seq.State);
 
         var (snap, _) = seq.Tick(0f, worldReady: false);
@@ -393,7 +462,9 @@ public sealed class TeleportAnimSequencerTests
         Assert.True(
             snap.ViewPlaneBlend > 0.95f,
             $"Expected ViewPlaneBlend near 1, got {snap.ViewPlaneBlend}");
-        Assert.True(snap.ViewPlaneBlend <= 1022f / 1024f);
+        Assert.True(
+            snap.ViewPlaneBlend
+                <= TeleportAnimSequencer.LastVisibleOutgoingAnimationLevel / 1024f);
     }
 
     [Fact]