test(examples): render hemplate views into buffers

Use hemplate render_into in public examples and example tests instead of the string-returning render helper, preserving SafeHtml wrapping only at the explicit effect boundary.

req: view/001

req: html_safety/002

examples/techdemo/src/lib.rs

@@ -40,11 +40,11 @@ mod tests {
 
     fn render_fast_metric(label: &'static str) -> SafeHtml {
         // req: html_safety/002 req: view/001
-        SafeHtml::trusted(
-            FastMetric { label }
-                .render()
-                .expect("techdemo fast metric renders"),
-        )
+        let mut html = String::new();
+        FastMetric { label }
+            .render_into(&mut html)
+            .expect("techdemo fast metric renders");
+        SafeHtml::trusted(html)
     }
 
     // req: examples/001 req: form/001 req: form/004 req: form/006 req: derive_handler/003

examples/techdemo/src/main.rs

@@ -549,7 +549,11 @@ fn render_control_center(page: ControlCenter) -> String {
 }
 
 fn render_template(template: &impl Hemplate) -> String {
-    template.render().expect("techdemo hemplate partial renders")
+    let mut html = String::new();
+    template
+        .render_into(&mut html)
+        .expect("techdemo hemplate partial renders");
+    html
 }
 
 fn render_html(template: &impl Hemplate) -> SafeHtml {