fix #427: sky drawn without fog like retail; world fog range is the keyframe's authored MinWorldFog/MaxWorldFog

Two April stand-ins, neither registered, met at the horizon from altitude as
a hard line between the dome's rim and the fog-coloured clear:

1. sky.frag fogged every non-additive sky layer with a 0.2 floor. Retail's
   GameSky::Draw @0x00506FF0 disables fixed-function fog around the whole
   sky draw unless an AdminEnvirons fog override is active (SetFFFogEnable(
   LScape::m_override_enabled ? 1 : 0)); additive layers stay unfogged via
   SetFFFogAlphaDisabled(1) at D3DPolyRender::SetSurface 0x59c882. The sky
   pass now sets ApplyFog only for (override active && !additive), with no
   floor.
2. WorldRenderFrameBuilder overwrote the authored fog range with one derived
   from the streaming window (538..2189 m always). Retail sets FOGSTART/
   FOGEND straight from the keyframe's MinWorldFog/MaxWorldFog
   (SkyDesc::GetWorldFog @0x00500CE0 -> SetFFFogProperties @0x005A2F70) with
   no draw-distance scaling; zfar is a constant 4000 m. The builder now
   leaves SceneLightingUbo.Build's values alone; ACDREAM_FOG_START_MULT /
   _END_MULT are deleted from RuntimeOptions.

Guards: SkyFogRuleTests (source-level, the sky renderer has no hermetic
harness); sky.frag.spv re-pinned in VulkanShaderManifestTests with the
reason. Research note 2026-04-23-sky-fog.md carries a correction banner.
App hermetic 6,070/0, Core 4,707/0 (Release). Owner look gate owed: night
and rain fog are now retail's shorter authored ranges.

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

src/AcDream.App/Rendering/Shaders/spv/shaders.manifest.json

@@ -316,7 +316,7 @@
         },
         {
           "stage": "frag",
-          "sourceSha256": "2ddf210d69b0c4a3c0870eecfb0ccba2097d93b365729739402bfe91e3b120d0",
+          "sourceSha256": "b1f3b924af2040c909337c02461ed6795b5320fb04b5bb371ce1546feead567c",
           "compiled": true
         }
       ]