test(core): RED -- doc_gate refuses the namespaced short-name alibi

Executable spec for the fieldtest spec_gap (decision on #316: tighten,
not ratify): doc_gate("lab316_nodes::Scale", "Scale") must be
Err(RestatesName) -- a doc normalizing to the final ::-segment of a
namespaced entry name restates the name. Unnamespaced entries and
genuine meaning lines containing the name stay Ok (guard assertions
green). Currently red: the shipped check compares the full name only.

refs #316

crates/aura-core/src/node.rs

@@ -811,6 +811,25 @@ mod tests {
         assert_eq!(doc_gate("rolling_max", "Rolling Max"), Err(DocGateFault::RestatesName));
     }
 
+    /// C29 tightening (#316 fieldtest): for a namespaced entry, the bare
+    /// display segment is a restatement too — a doc that adds nothing beyond
+    /// the name must not pass just because the name carries a `::` prefix.
+    /// Genuine meaning lines that merely *contain* the name stay legal.
+    #[test]
+    fn doc_gate_refuses_namespaced_short_name_restatement() {
+        // The most natural alibi at the extension-author seam: the node's
+        // own display name as its doc.
+        assert_eq!(doc_gate("lab316_nodes::Scale", "Scale"), Err(DocGateFault::RestatesName));
+        // Guard: a real meaning line stays Ok even when it contains the
+        // short name as a substring...
+        assert_eq!(
+            doc_gate("lab316_nodes::Scale", "scalar gain: emits the input times the factor param"),
+            Ok(())
+        );
+        // ...and a namespaced entry with a genuine doc is untouched.
+        assert_eq!(doc_gate("und::Opaque", "one-input f64 pass-through"), Ok(()));
+    }
+
     #[test]
     fn doc_gate_accepts_a_meaning_line() {
         assert_eq!(doc_gate("EMA", "exponential moving average over the input series"), Ok(()));