diag #181: root-cause chain complete - flapping cell 0x0181, wall-press excitation, and the REAL defect: camera-flood-scoped light application

Issue181VisFlapReplayTests: headless flood replay at the live parked pose names cell 0x8A020181 - +-0.5mm eye perturbations flip its admission (at yaw15/pitch-20 for every direction). Issue181CameraParkStabilityTests: the camera loop parks BIT-EXACT with static inputs (0.00um over 2000 frames) - the live ~1mm/frame wander is the wall-press equilibrium (sought steps a*gap ~4mm into the wall per frame, the clip lands within adjust_to_plane's parametric 0.02 window; player physics bit-frozen per [resolve]). That wobble is retail-class. The defect is OURS: the A7 adaptation scopes light application to the camera flood's per-frame admission, so a sliver cell flapping flips whole lit regions; retail computes light reach once at registration (Render::add_static_light -> CObjCell::add_lights), camera-independent. Fix direction: registration-time per-light reach sets via the portal graph (pseudocode docs/research/2026-07-06-a7-per-cell-lighting-pseudocode.md). ISSUES #181 updated with the full chain.

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

tests/AcDream.App.Tests/Rendering/Issue181CameraParkStabilityTests.cs

@@ -0,0 +1,100 @@
+using System;
+using System.Numerics;
+using AcDream.App.Rendering;
+using AcDream.Core.Rendering;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace AcDream.App.Tests.Rendering;
+
+/// <summary>
+/// #181 excitation probe — the live parked camera wanders ~0.9 mm/frame
+/// (launch-176-leakfix.log [flap-sweep]: 19,889 distinct sought values in 20k
+/// parked sweeps), which keeps the portal flood's knife-edge admissions
+/// flapping. Retail's parked viewer is a bit-exact fixed point (UpdateCamera
+/// dead-band `return viewer`).
+///
+/// This test drives RetailChaseCamera.Update with BIT-IDENTICAL inputs at the
+/// live frame rate: if the camera parks bit-stable here, the live wobble comes
+/// from its INPUTS (player position/yaw jitter out of GameWindow); if it
+/// wobbles here, the camera loop itself fails to reach the fixed point.
+/// </summary>
+public class Issue181CameraParkStabilityTests
+{
+    private readonly ITestOutputHelper _out;
+    public Issue181CameraParkStabilityTests(ITestOutputHelper output) => _out = output;
+
+    private sealed class PassthroughProbe : ICameraCollisionProbe
+    {
+        public CameraSweepResult SweepEye(Vector3 pivot, Vector3 desiredEye, uint cellId, uint selfEntityId, Vector3 playerPos)
+            => new(desiredEye, cellId);
+    }
+
+    [Fact]
+    public void ParkedCamera_StaticInputs_ReachesBitStableFixedPoint()
+    {
+        bool  savedAlign = CameraDiagnostics.AlignToSlope;
+        bool  savedColl  = CameraDiagnostics.CollideCamera;
+        float savedT     = CameraDiagnostics.TranslationStiffness;
+        float savedR     = CameraDiagnostics.RotationStiffness;
+        try
+        {
+            CameraDiagnostics.AlignToSlope         = true;   // production default
+            CameraDiagnostics.CollideCamera        = true;
+            CameraDiagnostics.TranslationStiffness = 0.45f;
+            CameraDiagnostics.RotationStiffness    = 0.45f;
+
+            var cam = new RetailChaseCamera { CollisionProbe = new PassthroughProbe() };
+
+            // Live-like parked pose: static player, static yaw, zero velocity,
+            // grounded on a flat contact plane, ~1500 fps.
+            var playerPos = new Vector3(49.5f, -39.9f, -5.9f);
+            float yaw     = 1.83f;
+            float dt      = 1f / 1500f;
+
+            void Step() => cam.Update(
+                playerPosition: playerPos,
+                playerYaw: yaw,
+                playerVelocity: Vector3.Zero,
+                isOnGround: true,
+                contactPlaneNormal: Vector3.UnitZ,
+                dt: dt,
+                cellId: 0x8A020142u,
+                selfEntityId: 0x5);
+
+            // Converge: at α≈0.003/frame the boom needs a few thousand frames
+            // to settle from the init pose into the dead-band.
+            for (int i = 0; i < 20000; i++) Step();
+
+            Vector3 a = cam.Position;
+            var fwdA = cam.View;   // full view matrix — includes the forward half
+
+            // 2000 further frames with bit-identical inputs: every one must be
+            // the exact fixed point (retail parks verbatim).
+            float maxDelta = 0f;
+            Vector3 prev = a;
+            bool viewChanged = false;
+            for (int i = 0; i < 2000; i++)
+            {
+                Step();
+                maxDelta = MathF.Max(maxDelta, Vector3.Distance(cam.Position, prev));
+                prev = cam.Position;
+                if (cam.View != fwdA) viewChanged = true;
+            }
+
+            _out.WriteLine(FormattableString.Invariant(
+                $"post-convergence maxConsecDelta={maxDelta * 1e6f:F2}um viewChanged={viewChanged} pos=({cam.Position.X:F7},{cam.Position.Y:F7},{cam.Position.Z:F7})"));
+
+            Assert.True(maxDelta == 0f,
+                $"parked camera must be a bit-exact fixed point, wandered up to {maxDelta * 1e6f:F1}um/frame");
+            Assert.False(viewChanged, "view matrix must be frozen at park");
+        }
+        finally
+        {
+            CameraDiagnostics.AlignToSlope         = savedAlign;
+            CameraDiagnostics.CollideCamera        = savedColl;
+            CameraDiagnostics.TranslationStiffness = savedT;
+            CameraDiagnostics.RotationStiffness    = savedR;
+        }
+    }
+}