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/gstd/src/render_node.rs

@@ -273,6 +273,7 @@ mod tests {
 				layout: layout.clone(),
 				lane_invariant: u32::MAX,
 				named_writes: Vec::new(),
+				named_reads: Vec::new(),
 			},
 		);
 		let GPoll::Final(result) = core_types::record::serve_input(&graph, &ctx, &frames) else {