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).
Add Weather::Type::STORM enum value and wire it from SMSG_WEATHER type 3.
Storm particles are faster (70 units/s vs rain's 50), wind-angled at 15+
units lateral velocity with gusty turbulence, darker blue-grey tint, and
shorter lifetime. Previously storms rendered identically to rain.
- 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
