Distant Horizons for VulkanMod

Hotfix — weather effects (rain, snow, particles) now render correctly in front of LODs on all GPUs. Fast clouds no longer render on top of LODs. Previously, the Phase 2 composite was overwriting weather pixels with LOD colors on NVIDIA and potentially other non-MoltenVK drivers.

• SSAO smoothing — enabled the bilateral Gaussian blur on SSAO output. Previously the blur was disabled (radius 0), causing visibly grainy/noisy ambient occlusion.
• Z-fighting fix (NONE mode) — added small depth bias to LOD depth output in NONE fade mode, preventing z-fighting at the MC/LOD overlap boundary.
• High-altitude LOD gap fix — LOD clip distance now uses 3D distance instead of XZ-only. Previously, flying high and looking down created a visible gap between MC terrain and LODs because the cylindrical XZ clip didn't match MC's spherical render distance.