test(examples): forbid direct slot render helper

Guard canonical examples against RenderSlotExt/.render(& usage so slot updates keep using generated lower-aware HTML paths.

req: component/003

req: runtime/001

req: examples/003

slhx-test/tests/examples_contract.rs

@@ -66,6 +66,8 @@ fn canonical_examples_do_not_author_low_level_resource_plumbing() {
         "HandlerRegistry",
         "InteractionForm",
         "register_handle(",
+        "RenderSlotExt",
+        ".render(&",
         "name=\"__h\"",
         "name='__h'",
     ];