feat(workout): hide registry conversion from golden path

Let the Workout generated interaction builder satisfy DispatchRegistry directly and guard canonical sources/docs against .into_registry() so the beginner path does not teach manual registry conversion.

req: examples/001

req: examples/006

req: public_api/002

hemx-test/tests/examples_contract.rs

@@ -64,6 +64,7 @@ fn canonical_examples_do_not_author_low_level_resource_plumbing() {
         "lower_html(",
         "render_html(",
         "HandlerRegistry",
+        ".into_registry()",
         "InteractionForm",
         "register_handle(",
         "SafeHtml",
@@ -180,6 +181,7 @@ fn canonical_example_docs_do_not_teach_low_level_plumbing() {
         "EffectBatch",
         "manual registry",
         "HandlerRegistry",
+        ".into_registry()",
         "InteractionForm",
         "register_handle(",
         "lower_html(",