feat(M03): add environment snapshot facade

RENDER.md

@@ -950,6 +950,20 @@ $exe = Join-Path $env:TEMP 'godot-4.6.1-openwc\Godot_v4.6.1-stable_win64.exe'
 - The ray height, 3x3 tile search and `2/5/10/20/40`-unit nearby fallback are
   preserved. No terrain geometry, cache, streaming or visual behavior changed.
 
+## 2026-07-16 World Environment Snapshot Facade
+
+- `WorldEnvironmentSnapshot` carries one immutable finite time-of-day value,
+  normalized to `[0, 24)` hours; invalid non-finite input is explicit.
+- `WorldRenderFacade.apply_environment_snapshot()` delegates the snapshot to the
+  scene-owned `WowSkyController`. The facade owns no `Environment`, sun, skybox,
+  shader global or DBC sampling state.
+- Checkpoint capture now submits its manifest time through the facade instead of
+  locating `WowSkyController` and mutating `use_system_time`, `time_speed` and
+  `fixed_time_hours` directly.
+- Applying a snapshot performs the same three fixed-clock assignments as the old
+  capture path. Light/Area/Skybox DBC lookup, interpolation, fog, sun and shader
+  behavior remain unchanged; weather and indoor environment state are follow-up work.
+
 ## Practical Rule For Future Work
 
 If something improves quality but creates visible hitch, it is not done. Move it to bake/cache/background work, split finalization over frames, or prewarm it before the player can see it.