docs(#79/#93): dat-truth check refutes the mesh-gate theory for missing fountain/candle particles

Same-session follow-up: user confirmed the light-carrier hydration fix
worked, then reported missing candle flames + fountain water particles.
Tested whether it's the same root cause (a mesh-empty Setup dropped by
EntityHydrationRules before its Setup.DefaultScript — the ambient
particle script GpuWorldState.cs:221 fires — is ever read). Refuted: the
fountain (0x02000AA3) has a surviving mesh part and a real DefaultScript
(0x33000B21), never dropped by the gate. The guessed "candle" objects
(0x02001967, ring of 16 around the fountain) have real mesh and no
DefaultScript at all — not candles. Separate root cause; filed as its
own issue rather than chased further this session.

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

tests/AcDream.Core.Tests/Rendering/Issue93TownNetworkFountainRoomLightInspectionTests.cs

@@ -134,4 +134,53 @@ public class Issue93TownNetworkFountainRoomLightInspectionTests
         _out.WriteLine($"  meshRefs survivor count = {survivors} (markerSkipped={markerSkipped} gfxNull={gfxNull}) " +
                        $"=> GameWindow.cs:7324 would {(survivors == 0 ? "DROP" : "KEEP")} this entity");
     }
+
+    /// <summary>
+    /// Follow-up (same session, 2026-07-09): user confirmed lighting improved but
+    /// reported missing candle flames + fountain water particles. Hypothesis tested:
+    /// same mesh-empty hydration-gate class as the light fix, just for
+    /// Setup.DefaultScript instead of Setup.Lights (GpuWorldState.cs:221 fires
+    /// ambient particle scripts from DefaultScript.DataId per hydrated entity — the
+    /// SAME lb.Entities list EntityHydrationRules.ShouldKeepEntity gates).
+    /// <b>REFUTED — do not re-chase this specific mechanism for #79/#93's particle
+    /// residual.</b> The fountain (0x02000AA3) has a SURVIVING mesh part (1/1) AND a
+    /// real DefaultScript (0x33000B21, almost certainly the water spray) — never
+    /// dropped by the gate, mesh or no. The "16 ring objects" guess (0x02001967) was
+    /// WRONG: real mesh, DefaultScript==0 — not candles, no script at all. Filed as
+    /// its own issue (missing ambient particles) — the remaining suspects are
+    /// downstream of hydration entirely: does EntityScriptActivator/
+    /// PhysicsScriptRunner actually fire DefaultScript=0x33000B21 for dat-hydrated
+    /// (ServerGuid==0) entities at runtime, does that script resolve to a real
+    /// PhysicsScriptTable entry, and does the resulting emitter reach the particle
+    /// renderer. NOT investigated further this session — separate root cause,
+    /// separate fix.
+    /// </summary>
+    [Theory]
+    [InlineData(0x02000AA3u)]   // the fountain itself (cell 0x00070144 center)
+    [InlineData(0x02001967u)]   // the 16 ring objects around the fountain (candles?)
+    [InlineData(0x020018C5u)]   // the other cell-center static
+    public void FountainAndCandleSetup_DefaultScriptAndMeshSurvivorCount_Dump(uint setupId)
+    {
+        var datDir = ResolveDatDir();
+        if (datDir is null) { _out.WriteLine("SKIP: no dat dir"); return; }
+        using var dats = new DatCollection(datDir, DatAccessType.Read);
+
+        var setup = dats.Get<Setup>(setupId);
+        Assert.NotNull(setup);
+
+        _out.WriteLine($"=== Setup 0x{setupId:X8}: Parts={setup!.Parts.Count} DefaultScript.DataId=0x{setup.DefaultScript.DataId:X8} Lights={setup.Lights.Count} ===");
+
+        var flat = AcDream.Core.Meshing.SetupMesh.Flatten(setup);
+        int survivors = 0;
+        foreach (var mr in flat)
+        {
+            if (AcDream.Core.Meshing.GfxObjDegradeResolver.IsRuntimeHiddenMarker(dats, mr.GfxObjId)) continue;
+            if (dats.Get<GfxObj>(mr.GfxObjId) is null) continue;
+            survivors++;
+        }
+        bool wouldBeKeptByCurrentFix = AcDream.Core.Meshing.EntityHydrationRules.ShouldKeepEntity(survivors, setup.Lights.Count);
+        _out.WriteLine($"  flattened={flat.Count} meshSurvivors={survivors} " +
+                       $"hasDefaultScript={setup.DefaultScript.DataId != 0} " +
+                       $"=> current ShouldKeepEntity(mesh,lights) = {wouldBeKeptByCurrentFix}");
+    }
 }