Optimize volumetric nebula rendering

Build the 64-bit client from merged REM-Client 5ff7cb636d815f6e55771b7efdad34d4832570bc,
including the nebula optimization in 157b06aa2f0b7be6ebc4ed2bd207ddfc6a706a55.

Smoothly merge self-shadow probes according to the integration footprint,
prepare pair metadata once on the CPU, and keep a direct path for nearby probes.
Retain cloud density, resolution and the first lighting/flicker fixes.

Synthetic RTX 2050 / 1080p cloud-pass measurements: distant 9.11 -> 8.19 ms
(-10.1%), rim 55.69 -> 52.82 ms (-5.2%), inside essentially unchanged.
Single synthetic runs; whole-game multiplayer FPS is not established.

Rebuild with MSVC Release|x64 under Wine and refresh the distributed runtime.
Keep the existing new-rem-client missions, ART assets and material data.
Verify 11,141 runtime/data files against the Lutris installation; saves unchanged.

RP8.dll SHA-256: 5275c77b53179e45daebf3f2c8fbb6d9fa4738f2470bb305ffba95ab35bcd50e.

BUILD_INFO.txt

@@ -1,6 +1,6 @@
-REM renderer update (64-bit)
-mod base: 5d3466fe459790c2824ce7a51eebe3646b621bfb
-renderer source: b0d47563bfbc08a36e1e74c7a876a0d02270fea9
-renderer build: OK - MSVC Release|x64
-renderer sha256: 614b64e7b507c255ba23d03e0c594a8db360148ce43d9d618b377dc4176b1f51
-scope: renderer only; existing new-rem-client runtime and missions retained
+REM-Client test build (64-bit)
+date:    2026-11-08 01:22
+commit:  5ff7cb6 (main)
+subject: Aktuellen main mit den Nebelkorrekturen zusammenführen
+tree:    clean
+build:   OK