RayTrace ShaderPack

## v3

### Fixed
- Temporal accumulation for reflections/GI was a complete no-op — history
  buffers were being cleared to zero every frame by default; added the
  missing `clear.colortex4/5 = false`, plus a first-frame ramp-in guard.
- Water rendered fully opaque instead of translucent — material ID was
  sharing the alpha channel used for GL blending. Moved it to a different
  channel so real translucency alpha is preserved.
- Hard shadows (Low profile, 1 sample) had a small diagonal sampling bias.
- Fragments outside the shadow map's range picked up edge-clamp artifacts
  instead of being treated as fully lit.
- Water gbuffer wrote bogus normals for near-invisible edge pixels, which
  the reflection ray marcher then treated as solid geometry.
- Deduplicated a `getViewPos()` helper that existed as two independently
  maintained copies.