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

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crates/engine/src/lib.rs

@@ -10,6 +10,10 @@
 //! run them off the UI thread.
 #![forbid(unsafe_code)]
 
+// Model/cache types remain available without linking the optional inference crate.
+#[cfg(not(feature = "denoise"))]
+extern crate lightcraft_denoise_core as lightcraft_denoise;
+
 pub mod availability;
 mod camera_preview;
 pub mod camera_profiles;