fix #28: port retail's sky default-script playback (aurora) and the particle facing law

The aurora was never missing data — it was a missing mechanism plus a
misread. New decompile evidence closes the April-2026 contradiction:
retail plays the sky carriers' PES through the Setup's own DefaultScript
(GameSky::MakeObject @0x00506EE0 -> CPhysicsObj::makeObject @0x00513970
sets state|=0x80000; animate_static_object @0x00513DF0 ticks
ScriptManager + ParticleManager). The pes_id column stays dead — that
half of the April finding stands; the ids are byte-equal mirrors.

- SkyPesFrameController is now the production owner (ACDREAM_ENABLE_SKY_PES
  deleted): script ids resolve from the Setup DefaultScript
  (SkyObjectData.DefaultScriptId; the pes_id column is a one-time-logged
  cross-check), slots persist by (index, gfx id, properties) per
  CreateDeletePhysicsObjects @0x005073C0 — a day-group swap keeping the
  carrier no longer restarts its emitters — and stale slots stop before
  replacements claim the slot-derived owner id.
- RetailParticleFacing ports calc_draw_frame @0x0050DFA0: degrade mode 2
  faces the viewer roll-free (set_vector_heading) instead of the camera
  plane; modes 3/4/5 spin the authored frame around one local axis
  (rotate_around_axis_to_vector) — Dereth authors 54 mode-5 emitters that
  previously got no facing at all; 1,583 mode-2 emitters get the exact
  law; authored/mode-1 paths are unchanged.
- The 2026-08-23 'whole-sky tint' was the Rainy-group lightning/thunder
  PES playing at the debug anchor inside their 0.03-0.19 window, not the
  aurora: the aurora is nine faint viewer-facing glows pulsing on
  6.7/15/55-minute rebirth cycles, in every day group, all day.

Research: docs/research/2026-08-23-sky-default-script-port.md.
Register: AD-112 filed (camera-anchored synthetic owners vs sky-cell
physics objects). ISSUES #2 corrected (the playback ban is lifted by the
new evidence); #28 fix landed pending the connected night gate.
Tests: RetailParticleFacingTests (16), SkyPesFrameControllerTests (6);
hermetic suites App 6,076/0, Core 4,905/0.

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

src/AcDream.Core/World/SkyDescLoader.cs

@@ -38,6 +38,22 @@ public sealed class SkyObjectData
     public uint  PesObjectId;
     public uint  Properties;
 
+    /// <summary>
+    /// The carrier Setup's own <c>DefaultScript</c> PES id (zero when the
+    /// gfx id is not a Setup or the Setup has none). This — not
+    /// <see cref="PesObjectId"/> — is what retail plays: a Setup with a
+    /// default script marks its physics object <c>state |= 0x80000</c>
+    /// (<c>CPhysicsObj::makeObject @0x00513970</c> →
+    /// <c>InitPartArrayObject</c>) and the static-animating tick
+    /// (<c>CPhysicsObj::animate_static_object @0x00513DF0</c>) drives
+    /// <c>ScriptManager::UpdateScripts</c> + the object's ParticleManager.
+    /// In Dereth's Region DAT the two ids are byte-equal for every sky
+    /// carrier (verified 2026-08-23); the dead <c>pes_id</c> column stays
+    /// parsed as a cross-check only. Full chain:
+    /// <c>docs/research/2026-08-23-sky-default-script-port.md</c>.
+    /// </summary>
+    public uint  DefaultScriptId;
+
     /// <summary>
     /// Source GfxObj sort centre. Celestial billboards are authored at their
     /// apparent direction from the camera, so transforming and normalizing
@@ -525,11 +541,40 @@ public static class SkyDescLoader
         GfxObjId     = s.DefaultGfxObjectId?.DataId ?? 0u,
         PesObjectId  = s.DefaultPesObjectId?.DataId ?? 0u,
         Properties   = s.Properties,
+        DefaultScriptId = ResolveSetupDefaultScript(
+            s.DefaultGfxObjectId?.DataId ?? 0u,
+            dats),
         AuthoredSortCenter = ResolveSortCenter(
             s.DefaultGfxObjectId?.DataId ?? 0u,
             dats),
     };
 
+    /// <summary>
+    /// Fetches a sky carrier Setup's <c>DefaultScript</c> id (the retail
+    /// sky-PES source — see <see cref="SkyObjectData.DefaultScriptId"/>).
+    /// Non-Setup ids (the dome, star layers, cloud sheets are raw GfxObjs)
+    /// and missing DATs resolve to zero.
+    /// </summary>
+    private static uint ResolveSetupDefaultScript(
+        uint gfxObjId,
+        IDatObjectSource? dats)
+    {
+        if (dats is null || (gfxObjId & 0xFF000000u) != 0x02000000u)
+            return 0u;
+
+        try
+        {
+            return dats.TryGet<Setup>(gfxObjId, out var setup) && setup is not null
+                ? setup.DefaultScript.DataId
+                : 0u;
+        }
+        catch
+        {
+            // Enhancement metadata cannot make authoritative sky loading fail.
+            return 0u;
+        }
+    }
+
     private static DatSkyKeyframeData ConvertTimeOfDay(
         SkyTimeOfDay s,
         IDatObjectSource? dats)