Create a VkPipelineCache at device init, loaded from disk if available.
All 65 pipeline creation calls across 19 renderer files now use the
shared cache. On shutdown, the cache is serialized to disk so subsequent
launches skip redundant shader compilation.
Cache path: ~/.local/share/wowee/pipeline_cache.bin (Linux),
~/Library/Caches/wowee/ (macOS), %APPDATA%\wowee\ (Windows).
Stale/corrupt caches are handled gracefully (fallback to empty cache).
- Skybox now uses DBC sky colors (skyTop/skyMiddle/skyBand1/skyBand2) instead
of hardcoded C++ color curves, with 3-band gradient and Rayleigh/Mie scattering
- Clouds receive sun direction for lit edges, self-shadowing, and silver lining
- Fixed sun quad box artifact with proper edge fade in celestial shader
- Lens flare attenuated by fog, cloud density, and weather intensity
- Replaced garish green/purple lens flare ghosts with warm natural palette
- Added zone-based weather system for single-player mode with per-zone rain/snow
configuration, probability-based activation, and smooth intensity transitions
- Server SMSG_WEATHER remains authoritative when connected to a server
Skybox: replace sphere-mesh approach with a fullscreen triangle that
reconstructs the world-space ray direction analytically via inverse
projection/view matrices. Eliminates clip.w=0 degeneracy at the horizon
and correctly maps altitude to dir.z in the Z-up coordinate system.
Clouds: hemisphere mesh was storing altitude in aPos.y (Y-up convention);
the Z-up view matrix projected this sideways, making clouds appear
vertical. Store altitude in aPos.z and update the fragment shader to
read dir.z as altitude and dir.xy as the horizontal UV plane.
