feat(prelude): export SafeHtml for page composition

Make the authoring prelude cover the SafeHtml page-fragment type so generated render/static_fragment helpers can compose without an extra core import.

req: dx/006

req: html_safety/002

slhx/src/lib.rs

@@ -82,7 +82,7 @@ pub mod prelude {
     pub use slhx_core::{
         navigate, push, redirect, replace, Atom, BuildFingerprint, ComponentRef, CssClass,
         CssClasses, Effect, EventName, Form, FormModel, FormValue, Handle, IntoEffect, KeyedSlot,
-        ParamName, Slot,
+        ParamName, SafeHtml, Slot,
     };
     pub use crate::{render, render_html, RenderKeyedSlotExt, RenderSlotExt};
     pub use slhx_derive::{app, component, form, handler, surface};
@@ -105,4 +105,14 @@ mod tests {
         assert_eq!(crate::render(&InlineView).as_str(), "<strong>ok</strong>");
         assert_eq!(crate::render_html(&InlineView).as_str(), "<strong>ok</strong>");
     }
+
+    #[test]
+    fn prelude_exports_safe_html_for_page_composition() {
+        // req: dx/006 req: html_safety/002
+        use crate::prelude::*;
+
+        let html = SafeHtml::join([render(&InlineView)]);
+
+        assert_eq!(html.as_str(), "<strong>ok</strong>");
+    }
 }