Resolve a named read's offset when the graph compiles

The fold already holds the name and the read input's finished layout, so
the offset falls out there rather than at construction: `RecordLayout`
carries the resolved numbers and `set_layout` copies them into the read
slots. Constructors are untouched, and census-marker reads keep their
current installation.

A read meets the value type the name was written at, so a disagreement
between a read here and a write upstream is the same graph error as two
writes disagreeing; the one-name-one-type check now spans reads and
writes together. An absent attribute stays absent and the read serves
the forced default rather than reporting it.

`read_attribute` is the catalog's get half, typed and never `Option` at
the kernel boundary, with the name declared exactly as the write side
declares it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

node-graph/nodes/math/src/lib.rs

@@ -1054,6 +1054,7 @@ mod graphene_test {
 	fn installed<N: Node<ContextImpl<'static>>>(mut node: N, layout: &Layout) -> N {
 		node.set_layout(core_types::record::RecordLayout {
 			named_writes: Vec::new(),
+			named_reads: Vec::new(),
 			frame_bytes: layout.frame_bytes(),
 			plan: Vec::new(),
 			layout: layout.clone(),
@@ -1116,6 +1117,7 @@ mod graphene_test {
 		let layout = out_layout::<bool>();
 		wired.set_layout(core_types::record::RecordLayout {
 			named_writes: Vec::new(),
+			named_reads: Vec::new(),
 			frame_bytes: layout.frame_bytes(),
 			plan: Vec::new(),
 			layout: layout.clone(),
@@ -1163,6 +1165,7 @@ mod graphene_test {
 		let layout = out_layout::<f64>();
 		wired.set_layout(core_types::record::RecordLayout {
 			named_writes: Vec::new(),
+			named_reads: Vec::new(),
 			frame_bytes: layout.frame_bytes(),
 			plan: Vec::new(),
 			layout: layout.clone(),