test(examples): guard docs against low-level plumbing

Extend the canonical example contract to scan Markdown docs so they keep teaching generated ergonomic APIs instead of raw handles, registry/form types, or legacy HTML helpers.

req: dx/002

req: dx/003

req: examples/003

slhx-test/tests/examples_contract.rs

@@ -99,6 +99,41 @@ fn canonical_examples_do_not_author_low_level_resource_plumbing() {
     assert!(failures.is_empty(), "{}", failures.join("\n"));
 }
 
+#[test]
+fn canonical_example_docs_do_not_teach_low_level_plumbing() {
+    // req: dx/002 req: dx/003 req: examples/003
+    let root = Path::new(env!("CARGO_MANIFEST_DIR")).parent().unwrap();
+    let examples = root.join("examples");
+    let forbidden = [
+        "generated handle ids",
+        "numeric handle ids",
+        "manual registry",
+        "HandlerRegistry",
+        "InteractionForm",
+        "register_handle(",
+        "lower_html(",
+        "render_html(",
+        "SafeHtml::trusted",
+    ];
+    let mut failures = Vec::new();
+    scan_examples(&examples, &mut |path, text| {
+        if path.extension().and_then(|ext| ext.to_str()) != Some("md") {
+            return;
+        }
+        for (line_no, line) in text.lines().enumerate() {
+            if let Some(token) = forbidden.iter().find(|token| line.contains(*token)) {
+                failures.push(format!(
+                    "{}:{}: example docs must teach generated ergonomic APIs, not `{token}`",
+                    path.display(),
+                    line_no + 1
+                ));
+            }
+        }
+    });
+
+    assert!(failures.is_empty(), "{}", failures.join("\n"));
+}
+
 #[test]
 fn browser_e2e_does_not_shortcut_product_interactions() {
     // req: examples/005
@@ -135,7 +170,7 @@ fn scan_examples(dir: &Path, visit: &mut impl FnMut(&Path, &str)) {
 fn is_example_source(path: &PathBuf) -> bool {
     matches!(
         path.extension().and_then(|ext| ext.to_str()),
-        Some("rs" | "heml" | "html")
+        Some("rs" | "heml" | "html" | "md")
     )
 }