Make documentation examples paste-ready for Objo Studio editors

Make copied code examples fit the Objo Studio editor they are intended for, and clearly identify where each example belongs.

When the documentation tells a reader to create or select an event handler or method and paste code into its body editor, the copyable block should contain only that editable body. It should not include a generated Sub, Function, or matching End declaration that Studio does not accept inside the body.

Examples that intentionally teach declaration syntax or show a complete member, class, module, or program should remain complete, but must be labelled so readers do not mistake them for body-editor snippets. The visible code and copied code must remain the same.