test(phys): A6.P5 RED — BFS from indoor cell doesn't reach door outdoor cell

Adds CellTransitTests with two A6P5_* unit tests:
  A6P5_BuildCellSetFromIndoorStart_ReachesDoorOutdoorCell  (RED — the bug)
  A6P5_BuildCellSetFromAlcove_AlsoReachesDoorOutdoorCell   (passes today)

The RED test reproduces the over-penetration tick's cellSet build:
sphere at (132.594, 16.350) in cell 0xA9B4013F, BFS portal-walks to
0xA9B40150 (alcove) but does NOT add the door's outdoor cell 0xA9B40029.
Pre-fix cellSet: 0xA9B4013F, 0xA9B40150, 0xA9B4014C — no outdoor cells.
Sphere wasn't straddling 0xA9B40150's exit portal so exitOutside stayed
false.

Also removes the 3 A6P5_* replay tests added to
DoorBugTrajectoryReplayTests in the previous commit (3253d84's
follow-up). Those tests didn't reproduce the bug — the harness's
BuildFaithfulDoorEngine has no cell fixtures, so cellSet returned empty
and GetNearbyObjects treated it as "no filter" → door always visible
→ over-penetration test trivially passed for the wrong reason. The
CellTransitTests version pins the bug at the BFS layer directly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Tests/Physics/DoorBugTrajectoryReplayTests.cs

@@ -1073,6 +1073,32 @@ public class DoorBugTrajectoryReplayTests
             "No captured record matched the predicate. Update the fixture.");
     }
 
+    /// <summary>
+    /// A6.P5 (2026-05-25) — loads one of the three fixed records from
+    /// <c>over-penetration-capture.jsonl</c> by index:
+    /// <list type="bullet">
+    ///   <item>0 — the over-penetration tick (cell-crossing 0xA9B4013F → 0xA9B40150)</item>
+    ///   <item>1 — stuck-position hit=yes variant (door fired)</item>
+    ///   <item>2 — stuck-position hit=no variant (door invisible — bug case)</item>
+    /// </list>
+    /// </summary>
+    private static ResolveCaptureRecord LoadOverPenRecord(int index)
+    {
+        var path = Path.Combine(FixtureDir, "over-penetration-capture.jsonl");
+        Assert.True(File.Exists(path),
+            $"A6.P5 over-penetration fixture missing: {path}. " +
+            $"Run tools/jsonl/extract-records.ps1 to rebuild.");
+
+        var lines = File.ReadAllLines(path);
+        Assert.True(lines.Length >= 3,
+            $"Expected >= 3 records in {path}; got {lines.Length}");
+
+        var raw = lines[index];
+        return System.Text.Json.JsonSerializer
+            .Deserialize<ResolveCaptureRecord>(raw,
+                CellarUpTrajectoryReplayTests.CaptureJsonOptions)!;
+    }
+
     /// <summary>
     /// Replays one captured ResolveWithTransition call against
     /// <paramref name="engine"/>, seeded with bodyBefore, and reports