LR-EDIT-DETAIL-DENOISE: address installation and model-policy review

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crates/gpu/src/lib.rs

@@ -29,7 +29,7 @@ use lightcraft_raster::Rgb32f;
 pub mod backend;
 #[cfg(not(target_arch = "wasm32"))]
 mod ctx;
-#[cfg(not(target_arch = "wasm32"))]
+#[cfg(all(feature = "denoise", not(target_arch = "wasm32")))]
 pub mod nn;
 #[cfg(not(target_arch = "wasm32"))]
 mod params;
@@ -149,7 +149,7 @@ pub fn enabled() -> bool {
 
 /// Why GPU compute that has a device of its own (denoise) is switched off by the user's settings, or `None`: the
 /// environment switches and the rendering preference, but not a render-device failure (the devices are separate).
-#[cfg(not(target_arch = "wasm32"))]
+#[cfg(all(feature = "denoise", not(target_arch = "wasm32")))]
 pub(crate) fn switched_off() -> Option<String> {
     if env_disabled() {
         return Some(if backend::env_off() { "disabled by LIGHTCRAFT_GPU_BACKEND=off" } else { "disabled by LIGHTCRAFT_GPU=0" }.into());