fix(selection): port SmartBox click lighting pulse

Port the retail high/low material-lighting cadence for successful world clicks, keep it instance-scoped in the modern renderer, and restore authored lighting after 0.8 seconds. Correct the selection oracle and pin timing plus per-frame buffer lifecycle with tests.

Co-authored-by: Codex <codex@openai.com>

src/AcDream.App/Rendering/Selection/RetailSelectionLightingPulse.cs

@@ -0,0 +1,101 @@
+using System.Diagnostics;
+
+namespace AcDream.App.Rendering.Selection;
+
+/// <summary>
+/// Replacement values passed by retail to CPhysicsObj::SetLighting.
+/// CMaterial receives luminosity first and diffuse second.
+/// </summary>
+internal readonly record struct RetailSelectionLighting(float Luminosity, float Diffuse)
+{
+    public static readonly RetailSelectionLighting Normal = new(0f, 1f);
+    public static readonly RetailSelectionLighting Low = new(0f, 0.35f);
+    public static readonly RetailSelectionLighting High = new(0.99f, 1f);
+}
+
+/// <summary>
+/// Retail SmartBox click-confirmation lighting pulse.
+///
+/// UIElement_SmartBoxWrapper::RecvNotice_SmartBoxObjectFound @ 0x004E5AD0
+/// applies HIGH immediately. Global_Loop @ 0x004E5620 then advances
+/// LOW/HIGH/LOW/RESTORE at 0.2-second intervals. A new click restores the old
+/// target implicitly and starts the sequence again on the new target.
+/// </summary>
+internal sealed class RetailSelectionLightingPulse
+{
+    internal const double FlipIntervalSeconds = 0.2;
+
+    private readonly Func<double> _now;
+    private uint _serverGuid;
+    private int _flipCount;
+    private double _nextFlip;
+    private RetailSelectionLighting _lighting;
+
+    public RetailSelectionLightingPulse(Func<double>? now = null)
+        => _now = now ?? MonotonicSeconds;
+
+    public void Start(uint serverGuid)
+    {
+        if (serverGuid == 0u)
+        {
+            Clear();
+            return;
+        }
+
+        _serverGuid = serverGuid;
+        _flipCount = 1;
+        _lighting = RetailSelectionLighting.High;
+        _nextFlip = _now() + FlipIntervalSeconds;
+    }
+
+    /// <summary>
+    /// Advances at most one flip per frame, matching retail Global_Loop. The
+    /// next deadline is based on the current frame time, so a long frame does
+    /// not replay multiple material mutations in one draw.
+    /// </summary>
+    public void Tick()
+    {
+        if (_flipCount == 0)
+            return;
+
+        double now = _now();
+        if (now < _nextFlip)
+            return;
+
+        int nextCount = _flipCount + 1;
+        if (nextCount >= 5)
+        {
+            Clear();
+            return;
+        }
+
+        _flipCount = nextCount;
+        _lighting = (nextCount & 1) != 0
+            ? RetailSelectionLighting.High
+            : RetailSelectionLighting.Low;
+        _nextFlip = now + FlipIntervalSeconds;
+    }
+
+    public bool TryGet(uint serverGuid, out RetailSelectionLighting lighting)
+    {
+        if (_flipCount != 0 && serverGuid != 0u && serverGuid == _serverGuid)
+        {
+            lighting = _lighting;
+            return true;
+        }
+
+        lighting = default;
+        return false;
+    }
+
+    public void Clear()
+    {
+        _serverGuid = 0u;
+        _flipCount = 0;
+        _nextFlip = 0d;
+        _lighting = default;
+    }
+
+    private static double MonotonicSeconds()
+        => Stopwatch.GetTimestamp() / (double)Stopwatch.Frequency;
+}