Fix remaining warnings

rend3-routine/src/forward.rs

@@ -25,6 +25,8 @@ use wgpu::{
 use crate::common::{CameraSpecifier, PerMaterialArchetypeInterface, WholeFrameInterfaces};
 use crate::uniforms::PerCameraUniform;
 
+/// This structure is unused.
+#[allow(dead_code)]  // This structure is never constructed
 #[derive(Serialize)]
 struct ForwardPreprocessingArguments {
     profile: Option<RendererProfile>,

rend3/src/instruction.rs

@@ -19,8 +19,15 @@ trait_supertrait_alias!(pub AddMaterialFillInvoke: FnOnce(&mut MaterialManager,
 trait_supertrait_alias!(pub ChangeMaterialChangeInvoke: FnOnce(&mut MaterialManager, &Device, &TextureManager<crate::types::Texture2DTag>, RawMaterialHandle) + WasmNotSend + WasmNotSync);
 trait_supertrait_alias!(pub AddGraphDataAddInvoke: FnOnce(&mut GraphStorage) + WasmNotSend);
 
+/// Instructions are the basic operations performed by the renderer.
+/// The user queues them up by making requests of Rend3,
+/// and they are all executed at the beginning
+/// of each frame render.
 pub struct Instruction {
+    /// The actual instruction item.
     pub kind: InstructionKind,
+    /// This field is not used.
+    #[allow(dead_code)]
     pub location: Location<'static>,
 }